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	$125.42	4.136%	$130.6074	$130.61	$130.60	$130.60
Purchase #2	$121.50	5.799%	$128.5458	$128.55	$128.55	$128.50
Purchase #3	$88.86	12.611%	$100.0661	$100.07	$100.05	$100.10
Purchase #4	$157.43	8.559%	$170.9044	$170.90	$170.90	$170.90
Purchase #5	$101.54	11.568%	$113.2861	$113.29	$113.30	$113.30
Purchase #6	$136.82	10.384%	$151.0274	$151.03	$151.05	$151.00
Purchase #7	$209.33	6.581%	$223.106	$223.11	$223.10	$223.10
7 purchase totals =	$940.90		$1,017.5432	$1,017.56	$1,017.55	$1,017.50