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	$135.93	7.413%	$146.0065	$146.01	$146.00	$146.00
Purchase #2	$101.69	9.654%	$111.5072	$111.51	$111.50	$111.50
Purchase #3	$49.56	5.872%	$52.4702	$52.47	$52.45	$52.50
Purchase #4	$123.28	4.838%	$129.2443	$129.24	$129.25	$129.20
Purchase #5	$88.78	12.434%	$99.8189	$99.82	$99.80	$99.80
Purchase #6	$84.67	10.497%	$93.5578	$93.56	$93.55	$93.60
Purchase #7	$226.66	10.448%	$250.3414	$250.34	$250.35	$250.30
7 purchase totals =	$810.57		$882.9463	$882.95	$882.90	$882.90