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	$80.25	13.307%	$90.9289	$90.93	$90.95	$90.90
Purchase #2	$30.25	7.350%	$32.4734	$32.47	$32.45	$32.50
Purchase #3	$191.91	5.191%	$201.872	$201.87	$201.85	$201.90
Purchase #4	$160.54	5.125%	$168.7677	$168.77	$168.75	$168.80
Purchase #5	$19.72	4.785%	$20.6636	$20.66	$20.65	$20.70
Purchase #6	$245.73	12.776%	$277.1245	$277.12	$277.10	$277.10
Purchase #7	$199.34	6.137%	$211.5735	$211.57	$211.55	$211.60
7 purchase totals =	$927.74		$1,003.4036	$1,003.39	$1,003.30	$1,003.50