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	$167.77	11.694%	$187.389	$187.39	$187.40	$187.40
Purchase #2	$103.76	8.528%	$112.6087	$112.61	$112.60	$112.60
Purchase #3	$170.46	6.759%	$181.9814	$181.98	$182.00	$182.00
Purchase #4	$42.51	4.729%	$44.5203	$44.52	$44.50	$44.50
Purchase #5	$213.92	7.546%	$230.0624	$230.06	$230.05	$230.10
Purchase #6	$37.36	11.647%	$41.7113	$41.71	$41.70	$41.70
Purchase #7	$226.59	12.546%	$255.018	$255.02	$255.00	$255.00
7 purchase totals =	$962.37		$1,053.2911	$1,053.29	$1,053.25	$1,053.30