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	$161.91	4.308%	$168.8851	$168.89	$168.90	$168.90
Purchase #2	$65.92	11.467%	$73.479	$73.48	$73.50	$73.50
Purchase #3	$193.37	3.714%	$200.5518	$200.55	$200.55	$200.60
Purchase #4	$107.42	4.687%	$112.4548	$112.45	$112.45	$112.50
Purchase #5	$243.89	13.456%	$276.7078	$276.71	$276.70	$276.70
Purchase #6	$150.86	7.665%	$162.4234	$162.42	$162.40	$162.40
Purchase #7	$233.76	6.570%	$249.118	$249.12	$249.10	$249.10
7 purchase totals =	$1,157.13		$1,243.6199	$1,243.62	$1,243.60	$1,243.70