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	$113.93	12.644%	$128.3353	$128.34	$128.35	$128.30
Purchase #2	$71.99	9.407%	$78.7621	$78.76	$78.75	$78.80
Purchase #3	$118.41	13.200%	$134.0401	$134.04	$134.05	$134.00
Purchase #4	$152.41	8.559%	$165.4548	$165.45	$165.45	$165.50
Purchase #5	$202.72	10.219%	$223.436	$223.44	$223.45	$223.40
Purchase #6	$183.74	13.753%	$209.0098	$209.01	$209.00	$209.00
Purchase #7	$185.26	10.365%	$204.4622	$204.46	$204.45	$204.50
7 purchase totals =	$1,028.46		$1,143.5003	$1,143.50	$1,143.50	$1,143.50