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	$44.46	9.116%	$48.513	$48.51	$48.50	$48.50
Purchase #2	$45.78	13.336%	$51.8852	$51.89	$51.90	$51.90
Purchase #3	$166.85	4.547%	$174.4367	$174.44	$174.45	$174.40
Purchase #4	$213.51	9.180%	$233.1102	$233.11	$233.10	$233.10
Purchase #5	$39.67	5.522%	$41.8606	$41.86	$41.85	$41.90
Purchase #6	$187.47	10.121%	$206.4438	$206.44	$206.45	$206.40
Purchase #7	$82.35	7.492%	$88.5197	$88.52	$88.50	$88.50
7 purchase totals =	$780.09		$844.7692	$844.77	$844.75	$844.70