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	$64.66	12.411%	$72.685	$72.69	$72.70	$72.70
Purchase #2	$71.30	7.549%	$76.6824	$76.68	$76.70	$76.70
Purchase #3	$106.53	3.855%	$110.6367	$110.64	$110.65	$110.60
Purchase #4	$164.43	7.199%	$176.2673	$176.27	$176.25	$176.30
Purchase #5	$178.43	6.642%	$190.2813	$190.28	$190.30	$190.30
Purchase #6	$140.42	7.197%	$150.526	$150.53	$150.55	$150.50
Purchase #7	$103.79	5.165%	$109.1508	$109.15	$109.15	$109.20
7 purchase totals =	$829.56		$886.2295	$886.24	$886.30	$886.30