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	$192.94	5.304%	$203.1735	$203.17	$203.15	$203.20
Purchase #2	$127.33	9.179%	$139.0176	$139.02	$139.00	$139.00
Purchase #3	$181.65	4.557%	$189.9278	$189.93	$189.95	$189.90
Purchase #4	$196.42	4.532%	$205.3218	$205.32	$205.30	$205.30
Purchase #5	$32.43	8.741%	$35.2647	$35.26	$35.25	$35.30
Purchase #6	$235.56	10.130%	$259.4222	$259.42	$259.40	$259.40
Purchase #7	$82.61	10.809%	$91.5393	$91.54	$91.55	$91.50
7 purchase totals =	$1,048.94		$1,123.6669	$1,123.66	$1,123.60	$1,123.60