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	$225.81	4.406%	$235.7592	$235.76	$235.75	$235.80
Purchase #2	$115.78	6.660%	$123.4909	$123.49	$123.50	$123.50
Purchase #3	$117.61	7.279%	$126.1708	$126.17	$126.15	$126.20
Purchase #4	$17.86	3.372%	$18.4622	$18.46	$18.45	$18.50
Purchase #5	$146.89	7.181%	$157.4382	$157.44	$157.45	$157.40
Purchase #6	$219.57	12.681%	$247.4137	$247.41	$247.40	$247.40
Purchase #7	$173.26	9.164%	$189.1375	$189.14	$189.15	$189.10
7 purchase totals =	$1,016.78		$1,097.8725	$1,097.87	$1,097.85	$1,097.90