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	$243.38	4.596%	$254.5657	$254.57	$254.55	$254.60
Purchase #2	$195.57	10.144%	$215.4086	$215.41	$215.40	$215.40
Purchase #3	$130.87	12.358%	$147.0429	$147.04	$147.05	$147.00
Purchase #4	$224.65	10.184%	$247.5284	$247.53	$247.55	$247.50
Purchase #5	$41.96	12.151%	$47.0586	$47.06	$47.05	$47.10
Purchase #6	$138.61	7.322%	$148.759	$148.76	$148.75	$148.80
Purchase #7	$33.32	11.431%	$37.1288	$37.13	$37.15	$37.10
7 purchase totals =	$1,008.36		$1,097.4920	$1,097.50	$1,097.50	$1,097.50