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	$172.76	8.272%	$187.0507	$187.05	$187.05	$187.10
Purchase #2	$234.85	9.228%	$256.522	$256.52	$256.50	$256.50
Purchase #3	$118.61	13.658%	$134.8098	$134.81	$134.80	$134.80
Purchase #4	$245.31	6.150%	$260.3966	$260.40	$260.40	$260.40
Purchase #5	$158.97	3.564%	$164.6357	$164.64	$164.65	$164.60
Purchase #6	$95.87	11.492%	$106.8874	$106.89	$106.90	$106.90
Purchase #7	$204.38	9.316%	$223.42	$223.42	$223.40	$223.40
7 purchase totals =	$1,230.75		$1,333.7222	$1,333.73	$1,333.70	$1,333.70