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	$223.89	11.870%	$250.4657	$250.47	$250.45	$250.50
Purchase #2	$5.77	13.691%	$6.56	$6.56	$6.55	$6.60
Purchase #3	$166.43	10.239%	$183.4708	$183.47	$183.45	$183.50
Purchase #4	$79.54	4.272%	$82.9379	$82.94	$82.95	$82.90
Purchase #5	$69.51	3.149%	$71.6989	$71.70	$71.70	$71.70
Purchase #6	$239.92	5.653%	$253.4827	$253.48	$253.50	$253.50
Purchase #7	$73.91	13.283%	$83.7275	$83.73	$83.75	$83.70
7 purchase totals =	$858.97		$932.3435	$932.35	$932.35	$932.40