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	$155.60	7.535%	$167.3245	$167.32	$167.30	$167.30
Purchase #2	$225.98	13.558%	$256.6184	$256.62	$256.60	$256.60
Purchase #3	$126.89	8.227%	$137.3292	$137.33	$137.35	$137.30
Purchase #4	$122.63	3.157%	$126.5014	$126.50	$126.50	$126.50
Purchase #5	$6.79	7.544%	$7.3022	$7.30	$7.30	$7.30
Purchase #6	$135.74	11.415%	$151.2347	$151.23	$151.25	$151.20
Purchase #7	$167.27	7.351%	$179.566	$179.57	$179.55	$179.60
7 purchase totals =	$940.90		$1,025.8764	$1,025.87	$1,025.85	$1,025.80