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	$171.42	11.715%	$191.5019	$191.50	$191.50	$191.50
Purchase #2	$68.53	5.445%	$72.2615	$72.26	$72.25	$72.30
Purchase #3	$188.95	5.402%	$199.1571	$199.16	$199.15	$199.20
Purchase #4	$98.76	9.644%	$108.2844	$108.28	$108.30	$108.30
Purchase #5	$140.41	7.133%	$150.4254	$150.43	$150.45	$150.40
Purchase #6	$221.80	10.412%	$244.8938	$244.89	$244.90	$244.90
Purchase #7	$68.73	4.710%	$71.9672	$71.97	$71.95	$72.00
7 purchase totals =	$958.60		$1,038.4913	$1,038.49	$1,038.50	$1,038.60