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	$135.55	9.815%	$148.8542	$148.85	$148.85	$148.90
Purchase #2	$134.59	5.377%	$141.8269	$141.83	$141.85	$141.80
Purchase #3	$232.53	13.267%	$263.3798	$263.38	$263.40	$263.40
Purchase #4	$32.94	8.384%	$35.7017	$35.70	$35.70	$35.70
Purchase #5	$171.64	9.593%	$188.1054	$188.11	$188.10	$188.10
Purchase #6	$86.36	6.142%	$91.6642	$91.66	$91.65	$91.70
Purchase #7	$119.31	3.358%	$123.3164	$123.32	$123.30	$123.30
7 purchase totals =	$912.92		$992.8486	$992.85	$992.85	$992.90