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	$217.49	13.828%	$247.5645	$247.56	$247.55	$247.60
Purchase #2	$55.59	11.205%	$61.8189	$61.82	$61.80	$61.80
Purchase #3	$221.76	8.499%	$240.6074	$240.61	$240.60	$240.60
Purchase #4	$53.69	7.248%	$57.5815	$57.58	$57.60	$57.60
Purchase #5	$180.56	5.419%	$190.3445	$190.34	$190.35	$190.30
Purchase #6	$240.53	12.236%	$269.9613	$269.96	$269.95	$270.00
Purchase #7	$153.91	12.806%	$173.6197	$173.62	$173.60	$173.60
7 purchase totals =	$1,123.53		$1,241.4978	$1,241.49	$1,241.45	$1,241.50