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	$78.90	3.695%	$81.8154	$81.82	$81.80	$81.80
Purchase #2	$129.98	8.693%	$141.2792	$141.28	$141.30	$141.30
Purchase #3	$187.47	10.130%	$206.4607	$206.46	$206.45	$206.50
Purchase #4	$82.75	10.359%	$91.3221	$91.32	$91.30	$91.30
Purchase #5	$146.75	7.833%	$158.2449	$158.24	$158.25	$158.20
Purchase #6	$178.68	6.287%	$189.9136	$189.91	$189.90	$189.90
Purchase #7	$245.76	7.203%	$263.4621	$263.46	$263.45	$263.50
7 purchase totals =	$1,050.29		$1,132.4980	$1,132.49	$1,132.45	$1,132.50