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	$174.64	12.287%	$196.098	$196.10	$196.10	$196.10
Purchase #2	$217.31	9.530%	$238.0196	$238.02	$238.00	$238.00
Purchase #3	$72.48	5.512%	$76.4751	$76.48	$76.50	$76.50
Purchase #4	$174.30	9.540%	$190.9282	$190.93	$190.95	$190.90
Purchase #5	$227.34	12.114%	$254.88	$254.88	$254.90	$254.90
Purchase #6	$231.61	3.530%	$239.7858	$239.79	$239.80	$239.80
Purchase #7	$218.64	6.784%	$233.4725	$233.47	$233.45	$233.50
7 purchase totals =	$1,316.32		$1,429.6592	$1,429.67	$1,429.70	$1,429.70