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	$143.30	3.387%	$148.1536	$148.15	$148.15	$148.20
Purchase #2	$92.92	8.819%	$101.1146	$101.11	$101.10	$101.10
Purchase #3	$116.40	6.134%	$123.54	$123.54	$123.55	$123.50
Purchase #4	$106.28	12.263%	$119.3131	$119.31	$119.30	$119.30
Purchase #5	$206.25	5.559%	$217.7154	$217.72	$217.70	$217.70
Purchase #6	$162.83	5.841%	$172.3409	$172.34	$172.35	$172.30
Purchase #7	$118.82	6.350%	$126.3651	$126.37	$126.35	$126.40
7 purchase totals =	$946.80		$1,008.5427	$1,008.54	$1,008.50	$1,008.50