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	$67.98	11.550%	$75.8317	$75.83	$75.85	$75.80
Purchase #2	$95.43	13.560%	$108.3703	$108.37	$108.35	$108.40
Purchase #3	$171.79	13.743%	$195.3991	$195.40	$195.40	$195.40
Purchase #4	$131.30	12.692%	$147.9646	$147.96	$147.95	$148.00
Purchase #5	$148.93	11.125%	$165.4985	$165.50	$165.50	$165.50
Purchase #6	$230.81	4.236%	$240.5871	$240.59	$240.60	$240.60
Purchase #7	$67.52	6.273%	$71.7555	$71.76	$71.75	$71.80
7 purchase totals =	$913.76		$1,005.4068	$1,005.41	$1,005.40	$1,005.50