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	$33.55	5.129%	$35.2708	$35.27	$35.25	$35.30
Purchase #2	$72.57	13.836%	$82.6108	$82.61	$82.60	$82.60
Purchase #3	$213.69	6.842%	$228.3107	$228.31	$228.30	$228.30
Purchase #4	$189.91	4.496%	$198.4484	$198.45	$198.45	$198.40
Purchase #5	$204.60	3.546%	$211.8551	$211.86	$211.85	$211.90
Purchase #6	$136.73	3.445%	$141.4403	$141.44	$141.45	$141.40
Purchase #7	$30.33	12.335%	$34.0712	$34.07	$34.05	$34.10
7 purchase totals =	$881.38		$932.0073	$932.01	$931.95	$932.00