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	$172.68	9.777%	$189.5629	$189.56	$189.55	$189.60
Purchase #2	$191.45	11.607%	$213.6716	$213.67	$213.65	$213.70
Purchase #3	$127.50	9.669%	$139.828	$139.83	$139.85	$139.80
Purchase #4	$58.73	10.144%	$64.6876	$64.69	$64.70	$64.70
Purchase #5	$222.70	11.417%	$248.1257	$248.13	$248.15	$248.10
Purchase #6	$232.82	9.530%	$255.0077	$255.01	$255.00	$255.00
Purchase #7	$64.27	13.108%	$72.6945	$72.69	$72.70	$72.70
7 purchase totals =	$1,070.15		$1,183.5780	$1,183.58	$1,183.60	$1,183.60