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	$133.61	12.396%	$150.1723	$150.17	$150.15	$150.20
Purchase #2	$63.35	5.528%	$66.852	$66.85	$66.85	$66.90
Purchase #3	$176.67	12.139%	$198.116	$198.12	$198.10	$198.10
Purchase #4	$156.75	10.616%	$173.3906	$173.39	$173.40	$173.40
Purchase #5	$46.98	3.148%	$48.4589	$48.46	$48.45	$48.50
Purchase #6	$89.95	13.752%	$102.3199	$102.32	$102.30	$102.30
Purchase #7	$223.51	9.272%	$244.2338	$244.23	$244.25	$244.20
7 purchase totals =	$890.82		$983.5435	$983.54	$983.50	$983.60