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	$211.33	6.216%	$224.4663	$224.47	$224.45	$224.50
Purchase #2	$160.95	4.555%	$168.2813	$168.28	$168.30	$168.30
Purchase #3	$181.77	6.485%	$193.5578	$193.56	$193.55	$193.60
Purchase #4	$61.65	12.487%	$69.3482	$69.35	$69.35	$69.30
Purchase #5	$146.94	12.453%	$165.2384	$165.24	$165.25	$165.20
Purchase #6	$68.75	4.391%	$71.7688	$71.77	$71.75	$71.80
Purchase #7	$79.47	4.206%	$82.8125	$82.81	$82.80	$82.80
7 purchase totals =	$910.86		$975.4733	$975.48	$975.45	$975.50