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	$94.53	5.618%	$99.8407	$99.84	$99.85	$99.80
Purchase #2	$41.90	12.123%	$46.9795	$46.98	$47.00	$47.00
Purchase #3	$213.46	13.544%	$242.371	$242.37	$242.35	$242.40
Purchase #4	$82.75	9.466%	$90.5831	$90.58	$90.60	$90.60
Purchase #5	$225.28	10.158%	$248.1639	$248.16	$248.15	$248.20
Purchase #6	$141.76	3.639%	$146.9186	$146.92	$146.90	$146.90
Purchase #7	$173.84	7.105%	$186.1913	$186.19	$186.20	$186.20
7 purchase totals =	$973.52		$1,061.0481	$1,061.04	$1,061.05	$1,061.10