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	$136.42	11.826%	$152.553	$152.55	$152.55	$152.60
Purchase #2	$165.68	8.630%	$179.9782	$179.98	$180.00	$180.00
Purchase #3	$198.82	10.381%	$219.4595	$219.46	$219.45	$219.50
Purchase #4	$193.51	10.245%	$213.3351	$213.34	$213.35	$213.30
Purchase #5	$159.39	5.472%	$168.1118	$168.11	$168.10	$168.10
Purchase #6	$243.66	8.593%	$264.5977	$264.60	$264.60	$264.60
Purchase #7	$150.30	10.502%	$166.0845	$166.08	$166.10	$166.10
7 purchase totals =	$1,247.78		$1,364.1198	$1,364.12	$1,364.15	$1,364.20