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	$135.89	10.777%	$150.5349	$150.53	$150.55	$150.50
Purchase #2	$199.32	13.235%	$225.7	$225.70	$225.70	$225.70
Purchase #3	$98.99	4.352%	$103.298	$103.30	$103.30	$103.30
Purchase #4	$233.63	12.107%	$261.9156	$261.92	$261.90	$261.90
Purchase #5	$218.29	11.624%	$243.664	$243.66	$243.65	$243.70
Purchase #6	$114.69	10.345%	$126.5547	$126.55	$126.55	$126.60
Purchase #7	$33.50	12.171%	$37.5773	$37.58	$37.60	$37.60
7 purchase totals =	$1,034.31		$1,149.2445	$1,149.24	$1,149.25	$1,149.30