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	$161.82	6.335%	$172.0713	$172.07	$172.05	$172.10
Purchase #2	$19.42	12.117%	$21.7731	$21.77	$21.75	$21.80
Purchase #3	$90.28	11.372%	$100.5466	$100.55	$100.55	$100.50
Purchase #4	$132.98	5.559%	$140.3724	$140.37	$140.35	$140.40
Purchase #5	$147.86	5.403%	$155.8489	$155.85	$155.85	$155.80
Purchase #6	$138.55	3.116%	$142.8672	$142.87	$142.85	$142.90
Purchase #7	$32.73	11.755%	$36.5774	$36.58	$36.60	$36.60
7 purchase totals =	$723.64		$770.0569	$770.06	$770.00	$770.10