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	$58.51	4.782%	$61.3079	$61.31	$61.30	$61.30
Purchase #2	$76.61	3.822%	$79.538	$79.54	$79.55	$79.50
Purchase #3	$225.41	11.562%	$251.4719	$251.47	$251.45	$251.50
Purchase #4	$68.92	13.399%	$78.1546	$78.15	$78.15	$78.20
Purchase #5	$145.75	13.718%	$165.744	$165.74	$165.75	$165.70
Purchase #6	$58.32	11.311%	$64.9166	$64.92	$64.90	$64.90
Purchase #7	$202.89	3.370%	$209.7274	$209.73	$209.75	$209.70
7 purchase totals =	$836.41		$910.8604	$910.86	$910.85	$910.80