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	$65.74	9.321%	$71.8676	$71.87	$71.85	$71.90
Purchase #2	$62.88	3.580%	$65.1311	$65.13	$65.15	$65.10
Purchase #3	$103.74	7.316%	$111.3296	$111.33	$111.35	$111.30
Purchase #4	$131.46	12.579%	$147.9964	$148.00	$148.00	$148.00
Purchase #5	$193.58	3.444%	$200.2469	$200.25	$200.25	$200.20
Purchase #6	$65.56	11.224%	$72.9185	$72.92	$72.90	$72.90
Purchase #7	$230.79	12.594%	$259.8557	$259.86	$259.85	$259.90
7 purchase totals =	$853.75		$929.3458	$929.36	$929.35	$929.30