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	$58.94	9.358%	$64.4556	$64.46	$64.45	$64.50
Purchase #2	$209.78	4.442%	$219.0984	$219.10	$219.10	$219.10
Purchase #3	$223.99	11.663%	$250.114	$250.11	$250.10	$250.10
Purchase #4	$172.83	13.484%	$196.1344	$196.13	$196.15	$196.10
Purchase #5	$216.72	6.267%	$230.3018	$230.30	$230.30	$230.30
Purchase #6	$58.76	3.817%	$61.0029	$61.00	$61.00	$61.00
Purchase #7	$116.55	3.112%	$120.177	$120.18	$120.20	$120.20
7 purchase totals =	$1,057.57		$1,141.2841	$1,141.28	$1,141.30	$1,141.30