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	$175.61	11.782%	$196.3004	$196.30	$196.30	$196.30
Purchase #2	$180.82	13.530%	$205.2849	$205.28	$205.30	$205.30
Purchase #3	$116.64	11.357%	$129.8868	$129.89	$129.90	$129.90
Purchase #4	$158.86	6.121%	$168.5838	$168.58	$168.60	$168.60
Purchase #5	$93.87	3.681%	$97.3254	$97.33	$97.35	$97.30
Purchase #6	$79.87	10.675%	$88.3961	$88.40	$88.40	$88.40
Purchase #7	$205.99	9.576%	$225.7156	$225.72	$225.70	$225.70
7 purchase totals =	$1,011.66		$1,111.4930	$1,111.50	$1,111.55	$1,111.50