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	$35.39	6.518%	$37.6967	$37.70	$37.70	$37.70
Purchase #2	$138.59	3.825%	$143.8911	$143.89	$143.90	$143.90
Purchase #3	$211.61	7.631%	$227.758	$227.76	$227.75	$227.80
Purchase #4	$152.96	13.656%	$173.8482	$173.85	$173.85	$173.80
Purchase #5	$110.46	8.468%	$119.8138	$119.81	$119.80	$119.80
Purchase #6	$165.87	8.673%	$180.2559	$180.26	$180.25	$180.30
Purchase #7	$160.50	11.105%	$178.3235	$178.32	$178.30	$178.30
7 purchase totals =	$975.38		$1,061.5872	$1,061.59	$1,061.55	$1,061.60