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	$47.34	5.654%	$50.0166	$50.02	$50.00	$50.00
Purchase #2	$219.72	10.526%	$242.8477	$242.85	$242.85	$242.80
Purchase #3	$214.53	13.721%	$243.9657	$243.97	$243.95	$244.00
Purchase #4	$61.51	9.822%	$67.5515	$67.55	$67.55	$67.60
Purchase #5	$196.83	13.300%	$223.0084	$223.01	$223.00	$223.00
Purchase #6	$198.39	5.229%	$208.7638	$208.76	$208.75	$208.80
Purchase #7	$168.62	12.283%	$189.3316	$189.33	$189.35	$189.30
7 purchase totals =	$1,106.94		$1,225.4853	$1,225.49	$1,225.45	$1,225.50