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	$194.36	10.345%	$214.4665	$214.47	$214.45	$214.50
Purchase #2	$58.25	13.555%	$66.1458	$66.15	$66.15	$66.10
Purchase #3	$158.25	4.448%	$165.289	$165.29	$165.30	$165.30
Purchase #4	$67.73	8.268%	$73.3299	$73.33	$73.35	$73.30
Purchase #5	$59.49	10.616%	$65.8055	$65.81	$65.80	$65.80
Purchase #6	$148.62	12.753%	$167.5735	$167.57	$167.55	$167.60
Purchase #7	$59.63	3.691%	$61.8309	$61.83	$61.85	$61.80
7 purchase totals =	$746.33		$814.4411	$814.45	$814.45	$814.40