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	$141.63	10.292%	$156.2066	$156.21	$156.20	$156.20
Purchase #2	$188.45	11.301%	$209.7467	$209.75	$209.75	$209.70
Purchase #3	$182.36	7.467%	$195.9768	$195.98	$196.00	$196.00
Purchase #4	$170.91	6.155%	$181.4295	$181.43	$181.45	$181.40
Purchase #5	$118.99	10.678%	$131.6958	$131.70	$131.70	$131.70
Purchase #6	$57.85	13.371%	$65.5851	$65.59	$65.60	$65.60
Purchase #7	$44.72	9.335%	$48.8946	$48.89	$48.90	$48.90
7 purchase totals =	$904.91		$989.5351	$989.55	$989.60	$989.50