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	$169.46	3.718%	$175.7605	$175.76	$175.75	$175.80
Purchase #2	$216.62	6.763%	$231.27	$231.27	$231.25	$231.30
Purchase #3	$86.62	4.114%	$90.1835	$90.18	$90.20	$90.20
Purchase #4	$158.50	4.482%	$165.604	$165.60	$165.60	$165.60
Purchase #5	$112.45	6.134%	$119.3477	$119.35	$119.35	$119.30
Purchase #6	$192.44	9.313%	$210.3619	$210.36	$210.35	$210.40
Purchase #7	$160.25	13.156%	$181.3325	$181.33	$181.35	$181.30
7 purchase totals =	$1,096.34		$1,173.8601	$1,173.85	$1,173.85	$1,173.90