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	$172.68	3.838%	$179.3075	$179.31	$179.30	$179.30
Purchase #2	$100.46	10.843%	$111.3529	$111.35	$111.35	$111.40
Purchase #3	$58.67	4.827%	$61.502	$61.50	$61.50	$61.50
Purchase #4	$166.83	9.522%	$182.7156	$182.72	$182.70	$182.70
Purchase #5	$83.57	7.328%	$89.694	$89.69	$89.70	$89.70
Purchase #6	$146.52	4.411%	$152.983	$152.98	$153.00	$153.00
Purchase #7	$94.57	3.823%	$98.1854	$98.19	$98.20	$98.20
7 purchase totals =	$823.30		$875.7404	$875.74	$875.75	$875.80