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	$107.37	3.698%	$111.3405	$111.34	$111.35	$111.30
Purchase #2	$158.73	13.616%	$180.3427	$180.34	$180.35	$180.30
Purchase #3	$121.96	13.481%	$138.4014	$138.40	$138.40	$138.40
Purchase #4	$38.72	9.220%	$42.29	$42.29	$42.30	$42.30
Purchase #5	$99.45	6.266%	$105.6815	$105.68	$105.70	$105.70
Purchase #6	$127.85	10.732%	$141.5709	$141.57	$141.55	$141.60
Purchase #7	$250.87	10.317%	$276.7523	$276.75	$276.75	$276.80
7 purchase totals =	$904.95		$996.3793	$996.37	$996.40	$996.40