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	$135.83	6.572%	$144.7567	$144.76	$144.75	$144.80
Purchase #2	$160.56	4.710%	$168.1224	$168.12	$168.10	$168.10
Purchase #3	$90.73	5.566%	$95.78	$95.78	$95.80	$95.80
Purchase #4	$243.68	4.112%	$253.7001	$253.70	$253.70	$253.70
Purchase #5	$80.56	9.327%	$88.0738	$88.07	$88.05	$88.10
Purchase #6	$89.29	6.528%	$95.1189	$95.12	$95.10	$95.10
Purchase #7	$200.60	3.698%	$208.0182	$208.02	$208.00	$208.00
7 purchase totals =	$1,001.25		$1,053.5701	$1,053.57	$1,053.50	$1,053.60