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	$232.75	13.487%	$264.141	$264.14	$264.15	$264.10
Purchase #2	$91.97	6.694%	$98.1265	$98.13	$98.15	$98.10
Purchase #3	$232.57	11.731%	$259.8528	$259.85	$259.85	$259.90
Purchase #4	$114.44	13.265%	$129.6205	$129.62	$129.60	$129.60
Purchase #5	$49.29	9.333%	$53.8902	$53.89	$53.90	$53.90
Purchase #6	$250.89	7.389%	$269.4283	$269.43	$269.45	$269.40
Purchase #7	$35.90	4.814%	$37.6282	$37.63	$37.65	$37.60
7 purchase totals =	$1,007.81		$1,112.6875	$1,112.69	$1,112.75	$1,112.60