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	$204.65	5.761%	$216.4399	$216.44	$216.45	$216.40
Purchase #2	$250.29	5.665%	$264.4689	$264.47	$264.45	$264.50
Purchase #3	$44.72	5.355%	$47.1148	$47.11	$47.10	$47.10
Purchase #4	$157.48	11.705%	$175.913	$175.91	$175.90	$175.90
Purchase #5	$223.55	8.141%	$241.7492	$241.75	$241.75	$241.70
Purchase #6	$41.77	7.429%	$44.8731	$44.87	$44.85	$44.90
Purchase #7	$80.45	11.573%	$89.7605	$89.76	$89.75	$89.80
7 purchase totals =	$1,002.91		$1,080.3194	$1,080.31	$1,080.25	$1,080.30