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	$44.25	8.657%	$48.0807	$48.08	$48.10	$48.10
Purchase #2	$164.98	12.348%	$185.3517	$185.35	$185.35	$185.40
Purchase #3	$42.51	7.867%	$45.8543	$45.85	$45.85	$45.90
Purchase #4	$188.57	4.144%	$196.3843	$196.38	$196.40	$196.40
Purchase #5	$229.86	11.810%	$257.0065	$257.01	$257.00	$257.00
Purchase #6	$130.89	3.605%	$135.6086	$135.61	$135.60	$135.60
Purchase #7	$77.69	6.639%	$82.8478	$82.85	$82.85	$82.80
7 purchase totals =	$878.75		$951.1339	$951.13	$951.15	$951.20