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	$205.94	11.351%	$229.3162	$229.32	$229.30	$229.30
Purchase #2	$55.68	9.634%	$61.0442	$61.04	$61.05	$61.00
Purchase #3	$89.96	6.607%	$95.9037	$95.90	$95.90	$95.90
Purchase #4	$135.77	7.761%	$146.3071	$146.31	$146.30	$146.30
Purchase #5	$68.94	4.602%	$72.1126	$72.11	$72.10	$72.10
Purchase #6	$121.96	11.233%	$135.6598	$135.66	$135.65	$135.70
Purchase #7	$246.93	3.645%	$255.9306	$255.93	$255.95	$255.90
7 purchase totals =	$925.18		$996.2742	$996.27	$996.25	$996.20