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	$164.79	4.112%	$171.5662	$171.57	$171.55	$171.60
Purchase #2	$89.65	13.319%	$101.5905	$101.59	$101.60	$101.60
Purchase #3	$203.53	9.867%	$223.6123	$223.61	$223.60	$223.60
Purchase #4	$158.98	6.295%	$168.9878	$168.99	$169.00	$169.00
Purchase #5	$98.41	10.461%	$108.7047	$108.70	$108.70	$108.70
Purchase #6	$231.70	5.250%	$243.8643	$243.86	$243.85	$243.90
Purchase #7	$84.67	5.828%	$89.6046	$89.60	$89.60	$89.60
7 purchase totals =	$1,031.73		$1,107.9304	$1,107.92	$1,107.90	$1,108.00