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	$234.45	5.757%	$247.9473	$247.95	$247.95	$247.90
Purchase #2	$135.44	12.767%	$152.7316	$152.73	$152.75	$152.70
Purchase #3	$50.44	4.574%	$52.7471	$52.75	$52.75	$52.70
Purchase #4	$59.50	5.336%	$62.6749	$62.67	$62.65	$62.70
Purchase #5	$166.53	9.207%	$181.8624	$181.86	$181.85	$181.90
Purchase #6	$166.38	3.294%	$171.8606	$171.86	$171.85	$171.90
Purchase #7	$37.83	12.753%	$42.6545	$42.65	$42.65	$42.70
7 purchase totals =	$850.57		$912.4784	$912.47	$912.45	$912.50