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	$89.66	5.720%	$94.7886	$94.79	$94.80	$94.80
Purchase #2	$79.25	4.511%	$82.825	$82.83	$82.85	$82.80
Purchase #3	$37.50	5.314%	$39.4928	$39.49	$39.50	$39.50
Purchase #4	$169.66	7.753%	$182.8137	$182.81	$182.80	$182.80
Purchase #5	$32.46	13.148%	$36.7278	$36.73	$36.75	$36.70
Purchase #6	$242.25	8.366%	$262.5166	$262.52	$262.50	$262.50
Purchase #7	$158.28	13.519%	$179.6779	$179.68	$179.70	$179.70
7 purchase totals =	$809.06		$878.8424	$878.85	$878.90	$878.80