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	$174.60	6.259%	$185.5282	$185.53	$185.55	$185.50
Purchase #2	$211.56	3.433%	$218.8229	$218.82	$218.80	$218.80
Purchase #3	$129.73	5.480%	$136.8392	$136.84	$136.85	$136.80
Purchase #4	$207.64	3.791%	$215.5116	$215.51	$215.50	$215.50
Purchase #5	$200.65	9.360%	$219.4308	$219.43	$219.45	$219.40
Purchase #6	$158.31	12.786%	$178.5515	$178.55	$178.55	$178.60
Purchase #7	$170.40	7.328%	$182.8869	$182.89	$182.90	$182.90
7 purchase totals =	$1,252.89		$1,337.5711	$1,337.57	$1,337.60	$1,337.50