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	$102.46	6.567%	$109.1885	$109.19	$109.20	$109.20
Purchase #2	$151.72	13.480%	$172.1719	$172.17	$172.15	$172.20
Purchase #3	$54.75	10.704%	$60.6104	$60.61	$60.60	$60.60
Purchase #4	$133.89	10.214%	$147.5655	$147.57	$147.55	$147.60
Purchase #5	$124.46	3.246%	$128.5	$128.50	$128.50	$128.50
Purchase #6	$174.38	5.812%	$184.515	$184.52	$184.50	$184.50
Purchase #7	$200.59	11.226%	$223.1082	$223.11	$223.10	$223.10
7 purchase totals =	$942.25		$1,025.6595	$1,025.67	$1,025.60	$1,025.70