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	$124.53	6.443%	$132.5535	$132.55	$132.55	$132.60
Purchase #2	$154.43	11.379%	$172.0026	$172.00	$172.00	$172.00
Purchase #3	$160.39	13.158%	$181.4941	$181.49	$181.50	$181.50
Purchase #4	$214.87	6.641%	$229.1395	$229.14	$229.15	$229.10
Purchase #5	$205.48	8.272%	$222.4773	$222.48	$222.50	$222.50
Purchase #6	$215.41	11.387%	$239.9387	$239.94	$239.95	$239.90
Purchase #7	$33.33	4.618%	$34.8692	$34.87	$34.85	$34.90
7 purchase totals =	$1,108.44		$1,212.4749	$1,212.47	$1,212.50	$1,212.50