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	$32.45	3.461%	$33.5731	$33.57	$33.55	$33.60
Purchase #2	$157.58	4.363%	$164.4552	$164.46	$164.45	$164.50
Purchase #3	$141.78	6.838%	$151.4749	$151.47	$151.45	$151.50
Purchase #4	$149.88	12.393%	$168.4546	$168.45	$168.45	$168.50
Purchase #5	$127.80	8.524%	$138.6937	$138.69	$138.70	$138.70
Purchase #6	$218.36	12.285%	$245.1855	$245.19	$245.20	$245.20
Purchase #7	$34.35	3.335%	$35.4956	$35.50	$35.50	$35.50
7 purchase totals =	$862.20		$937.3326	$937.33	$937.30	$937.50