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	$100.94	12.122%	$113.1759	$113.18	$113.20	$113.20
Purchase #2	$239.90	7.398%	$257.6478	$257.65	$257.65	$257.60
Purchase #3	$111.93	3.838%	$116.2259	$116.23	$116.25	$116.20
Purchase #4	$170.72	12.324%	$191.7595	$191.76	$191.75	$191.80
Purchase #5	$137.91	6.334%	$146.6452	$146.65	$146.65	$146.60
Purchase #6	$96.68	3.572%	$100.1334	$100.13	$100.15	$100.10
Purchase #7	$155.97	9.780%	$171.2239	$171.22	$171.20	$171.20
7 purchase totals =	$1,014.05		$1,096.8116	$1,096.82	$1,096.85	$1,096.70