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	$177.83	10.605%	$196.6889	$196.69	$196.70	$196.70
Purchase #2	$56.45	13.585%	$64.1187	$64.12	$64.10	$64.10
Purchase #3	$232.43	7.766%	$250.4805	$250.48	$250.50	$250.50
Purchase #4	$81.75	7.787%	$88.1159	$88.12	$88.10	$88.10
Purchase #5	$37.25	9.290%	$40.7105	$40.71	$40.70	$40.70
Purchase #6	$82.44	8.608%	$89.5364	$89.54	$89.55	$89.50
Purchase #7	$235.43	3.619%	$243.9502	$243.95	$243.95	$244.00
7 purchase totals =	$903.58		$973.6011	$973.61	$973.60	$973.60