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	$89.55	5.558%	$94.5272	$94.53	$94.55	$94.50
Purchase #2	$124.89	13.624%	$141.905	$141.91	$141.90	$141.90
Purchase #3	$106.28	10.742%	$117.6966	$117.70	$117.70	$117.70
Purchase #4	$101.71	6.763%	$108.5886	$108.59	$108.60	$108.60
Purchase #5	$71.71	6.460%	$76.3425	$76.34	$76.35	$76.30
Purchase #6	$180.31	11.357%	$200.7878	$200.79	$200.80	$200.80
Purchase #7	$17.78	5.733%	$18.7993	$18.80	$18.80	$18.80
7 purchase totals =	$692.23		$758.6470	$758.66	$758.70	$758.60