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	$33.89	4.812%	$35.5208	$35.52	$35.50	$35.50
Purchase #2	$222.25	6.668%	$237.0696	$237.07	$237.05	$237.10
Purchase #3	$30.32	4.360%	$31.642	$31.64	$31.65	$31.60
Purchase #4	$160.30	13.869%	$182.532	$182.53	$182.55	$182.50
Purchase #5	$198.89	6.532%	$211.8815	$211.88	$211.90	$211.90
Purchase #6	$7.58	4.287%	$7.905	$7.91	$7.90	$7.90
Purchase #7	$222.29	3.595%	$230.2813	$230.28	$230.30	$230.30
7 purchase totals =	$875.52		$936.8322	$936.83	$936.85	$936.80