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	$61.49	12.457%	$69.1498	$69.15	$69.15	$69.10
Purchase #2	$124.52	13.394%	$141.1982	$141.20	$141.20	$141.20
Purchase #3	$165.98	8.163%	$179.5289	$179.53	$179.55	$179.50
Purchase #4	$164.39	12.816%	$185.4582	$185.46	$185.45	$185.50
Purchase #5	$186.39	13.468%	$211.493	$211.49	$211.50	$211.50
Purchase #6	$130.59	11.115%	$145.1051	$145.11	$145.10	$145.10
Purchase #7	$213.89	12.617%	$240.8765	$240.88	$240.90	$240.90
7 purchase totals =	$1,047.25		$1,172.8097	$1,172.82	$1,172.85	$1,172.80