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	$176.95	12.753%	$199.5164	$199.52	$199.50	$199.50
Purchase #2	$71.33	11.401%	$79.4623	$79.46	$79.45	$79.50
Purchase #3	$91.96	8.223%	$99.5219	$99.52	$99.50	$99.50
Purchase #4	$145.40	13.451%	$164.9578	$164.96	$164.95	$165.00
Purchase #5	$175.76	13.115%	$198.8109	$198.81	$198.80	$198.80
Purchase #6	$143.74	4.275%	$149.8849	$149.88	$149.90	$149.90
Purchase #7	$108.52	11.183%	$120.6558	$120.66	$120.65	$120.70
7 purchase totals =	$913.66		$1,012.8100	$1,012.81	$1,012.75	$1,012.90