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	$169.32	11.336%	$188.5141	$188.51	$188.50	$188.50
Purchase #2	$105.66	5.632%	$111.6108	$111.61	$111.60	$111.60
Purchase #3	$116.96	7.445%	$125.6677	$125.67	$125.65	$125.70
Purchase #4	$234.60	6.806%	$250.5669	$250.57	$250.55	$250.60
Purchase #5	$242.59	4.860%	$254.3799	$254.38	$254.40	$254.40
Purchase #6	$41.84	8.189%	$45.2663	$45.27	$45.25	$45.30
Purchase #7	$93.96	13.332%	$106.4867	$106.49	$106.50	$106.50
7 purchase totals =	$1,004.93		$1,082.4924	$1,082.50	$1,082.45	$1,082.60