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	$230.93	4.825%	$242.0724	$242.07	$242.05	$242.10
Purchase #2	$210.31	3.485%	$217.6393	$217.64	$217.65	$217.60
Purchase #3	$47.40	5.802%	$50.1501	$50.15	$50.15	$50.20
Purchase #4	$232.70	7.475%	$250.0943	$250.09	$250.10	$250.10
Purchase #5	$115.46	10.704%	$127.8188	$127.82	$127.80	$127.80
Purchase #6	$101.85	6.359%	$108.3266	$108.33	$108.35	$108.30
Purchase #7	$59.78	12.348%	$67.1616	$67.16	$67.15	$67.20
7 purchase totals =	$998.43		$1,063.2631	$1,063.26	$1,063.25	$1,063.30