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	$215.72	10.569%	$238.5194	$238.52	$238.50	$238.50
Purchase #2	$247.93	10.616%	$274.2502	$274.25	$274.25	$274.30
Purchase #3	$197.41	11.214%	$219.5476	$219.55	$219.55	$219.50
Purchase #4	$7.93	4.777%	$8.3088	$8.31	$8.30	$8.30
Purchase #5	$132.25	6.780%	$141.2166	$141.22	$141.20	$141.20
Purchase #6	$158.33	4.329%	$165.1841	$165.18	$165.20	$165.20
Purchase #7	$57.79	11.174%	$64.2475	$64.25	$64.25	$64.20
7 purchase totals =	$1,017.36		$1,111.2742	$1,111.28	$1,111.25	$1,111.20