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	$53.57	3.246%	$55.3089	$55.31	$55.30	$55.30
Purchase #2	$74.53	5.401%	$78.5554	$78.56	$78.55	$78.60
Purchase #3	$203.76	9.520%	$223.158	$223.16	$223.15	$223.20
Purchase #4	$78.62	4.355%	$82.0439	$82.04	$82.05	$82.00
Purchase #5	$122.88	3.282%	$126.9129	$126.91	$126.90	$126.90
Purchase #6	$249.83	12.706%	$281.5734	$281.57	$281.55	$281.60
Purchase #7	$204.93	7.651%	$220.6092	$220.61	$220.60	$220.60
7 purchase totals =	$988.12		$1,068.1617	$1,068.16	$1,068.10	$1,068.20