Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$171.25	7.279%	$183.7153	$183.72	$183.70	$183.70
Purchase #2	$168.46	3.618%	$174.5549	$174.55	$174.55	$174.60
Purchase #3	$239.86	6.138%	$254.5826	$254.58	$254.60	$254.60
Purchase #4	$244.50	13.574%	$277.6884	$277.69	$277.70	$277.70
Purchase #5	$249.38	11.801%	$278.8093	$278.81	$278.80	$278.80
Purchase #6	$152.95	3.604%	$158.4623	$158.46	$158.45	$158.50
Purchase #7	$154.91	11.312%	$172.4334	$172.43	$172.45	$172.40
7 purchase totals =	$1,381.31		$1,500.2462	$1,500.24	$1,500.25	$1,500.30