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	$94.80	6.252%	$100.7269	$100.73	$100.75	$100.70
Purchase #2	$201.56	5.598%	$212.8433	$212.84	$212.85	$212.80
Purchase #3	$243.77	7.793%	$262.767	$262.77	$262.75	$262.80
Purchase #4	$81.65	11.257%	$90.8413	$90.84	$90.85	$90.80
Purchase #5	$137.74	9.493%	$150.8157	$150.82	$150.80	$150.80
Purchase #6	$211.53	11.359%	$235.5577	$235.56	$235.55	$235.60
Purchase #7	$94.43	5.651%	$99.7662	$99.77	$99.75	$99.80
7 purchase totals =	$1,065.48		$1,153.3181	$1,153.33	$1,153.30	$1,153.30