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	$185.41	11.165%	$206.111	$206.11	$206.10	$206.10
Purchase #2	$212.45	4.821%	$222.6922	$222.69	$222.70	$222.70
Purchase #3	$213.69	11.548%	$238.3669	$238.37	$238.35	$238.40
Purchase #4	$172.59	7.268%	$185.1338	$185.13	$185.15	$185.10
Purchase #5	$192.37	9.765%	$211.1549	$211.15	$211.15	$211.20
Purchase #6	$165.94	5.748%	$175.4782	$175.48	$175.50	$175.50
Purchase #7	$67.78	6.375%	$72.101	$72.10	$72.10	$72.10
7 purchase totals =	$1,210.23		$1,311.0380	$1,311.03	$1,311.05	$1,311.10