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	$191.37	3.412%	$197.8995	$197.90	$197.90	$197.90
Purchase #2	$244.82	8.740%	$266.2173	$266.22	$266.20	$266.20
Purchase #3	$199.39	8.703%	$216.7429	$216.74	$216.75	$216.70
Purchase #4	$63.69	13.700%	$72.4155	$72.42	$72.40	$72.40
Purchase #5	$32.61	12.328%	$36.6302	$36.63	$36.65	$36.60
Purchase #6	$187.89	5.558%	$198.3329	$198.33	$198.35	$198.30
Purchase #7	$106.63	4.237%	$111.1479	$111.15	$111.15	$111.10
7 purchase totals =	$1,026.40		$1,099.3862	$1,099.39	$1,099.40	$1,099.20