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	$69.47	4.736%	$72.7601	$72.76	$72.75	$72.80
Purchase #2	$198.25	6.534%	$211.2037	$211.20	$211.20	$211.20
Purchase #3	$6.30	12.871%	$7.1109	$7.11	$7.10	$7.10
Purchase #4	$12.69	5.843%	$13.4315	$13.43	$13.45	$13.40
Purchase #5	$211.35	5.282%	$222.5135	$222.51	$222.50	$222.50
Purchase #6	$219.54	11.809%	$245.4655	$245.47	$245.45	$245.50
Purchase #7	$171.68	10.696%	$190.0429	$190.04	$190.05	$190.00
7 purchase totals =	$889.28		$962.5281	$962.52	$962.50	$962.50