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	$234.72	9.196%	$256.3049	$256.30	$256.30	$256.30
Purchase #2	$200.63	8.347%	$217.3766	$217.38	$217.40	$217.40
Purchase #3	$140.82	3.346%	$145.5318	$145.53	$145.55	$145.50
Purchase #4	$124.89	4.761%	$130.836	$130.84	$130.85	$130.80
Purchase #5	$22.43	8.732%	$24.3886	$24.39	$24.40	$24.40
Purchase #6	$98.44	4.745%	$103.111	$103.11	$103.10	$103.10
Purchase #7	$185.48	11.582%	$206.9623	$206.96	$206.95	$207.00
7 purchase totals =	$1,007.41		$1,084.5112	$1,084.51	$1,084.55	$1,084.50