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	$32.65	8.344%	$35.3743	$35.37	$35.35	$35.40
Purchase #2	$95.38	9.361%	$104.3085	$104.31	$104.30	$104.30
Purchase #3	$78.97	9.199%	$86.2345	$86.23	$86.25	$86.20
Purchase #4	$5.33	10.394%	$5.884	$5.88	$5.90	$5.90
Purchase #5	$176.91	5.204%	$186.1164	$186.12	$186.10	$186.10
Purchase #6	$45.68	5.388%	$48.1412	$48.14	$48.15	$48.10
Purchase #7	$54.54	8.785%	$59.3313	$59.33	$59.35	$59.30
7 purchase totals =	$489.46		$525.3902	$525.38	$525.40	$525.30