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	$103.42	6.809%	$110.4619	$110.46	$110.45	$110.50
Purchase #2	$121.44	8.508%	$131.7721	$131.77	$131.75	$131.80
Purchase #3	$50.47	9.277%	$55.1521	$55.15	$55.15	$55.20
Purchase #4	$51.59	5.143%	$54.2433	$54.24	$54.25	$54.20
Purchase #5	$167.58	6.294%	$178.1275	$178.13	$178.15	$178.10
Purchase #6	$84.45	6.836%	$90.223	$90.22	$90.20	$90.20
Purchase #7	$237.25	11.603%	$264.7781	$264.78	$264.80	$264.80
7 purchase totals =	$816.20		$884.7580	$884.75	$884.75	$884.80