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	$176.47	3.849%	$183.2623	$183.26	$183.25	$183.30
Purchase #2	$109.98	13.204%	$124.5018	$124.50	$124.50	$124.50
Purchase #3	$59.61	3.153%	$61.4895	$61.49	$61.50	$61.50
Purchase #4	$211.34	11.661%	$235.9844	$235.98	$236.00	$236.00
Purchase #5	$153.79	12.281%	$172.6769	$172.68	$172.70	$172.70
Purchase #6	$81.67	13.682%	$92.8441	$92.84	$92.85	$92.80
Purchase #7	$133.86	12.380%	$150.4319	$150.43	$150.45	$150.40
7 purchase totals =	$926.72		$1,021.1909	$1,021.18	$1,021.25	$1,021.20