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	$169.33	12.506%	$190.5064	$190.51	$190.50	$190.50
Purchase #2	$87.80	11.387%	$97.7978	$97.80	$97.80	$97.80
Purchase #3	$51.55	4.412%	$53.8244	$53.82	$53.80	$53.80
Purchase #4	$79.68	11.221%	$88.6209	$88.62	$88.60	$88.60
Purchase #5	$179.77	5.628%	$189.8875	$189.89	$189.90	$189.90
Purchase #6	$184.61	3.772%	$191.5735	$191.57	$191.55	$191.60
Purchase #7	$35.77	13.584%	$40.629	$40.63	$40.65	$40.60
7 purchase totals =	$788.51		$852.8395	$852.84	$852.80	$852.80