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	$208.52	7.838%	$224.8638	$224.86	$224.85	$224.90
Purchase #2	$109.34	13.776%	$124.4027	$124.40	$124.40	$124.40
Purchase #3	$183.55	7.160%	$196.6922	$196.69	$196.70	$196.70
Purchase #4	$136.77	12.166%	$153.4094	$153.41	$153.40	$153.40
Purchase #5	$132.40	10.270%	$145.9975	$146.00	$146.00	$146.00
Purchase #6	$93.27	8.626%	$101.3155	$101.32	$101.30	$101.30
Purchase #7	$48.45	10.280%	$53.4307	$53.43	$53.45	$53.40
7 purchase totals =	$912.30		$1,000.1118	$1,000.11	$1,000.10	$1,000.10