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	$82.49	13.335%	$93.49	$93.49	$93.50	$93.50
Purchase #2	$37.62	13.612%	$42.7408	$42.74	$42.75	$42.70
Purchase #3	$118.56	11.583%	$132.2928	$132.29	$132.30	$132.30
Purchase #4	$89.47	12.683%	$100.8175	$100.82	$100.80	$100.80
Purchase #5	$90.40	6.194%	$95.9994	$96.00	$96.00	$96.00
Purchase #6	$97.59	3.593%	$101.0964	$101.10	$101.10	$101.10
Purchase #7	$118.32	13.404%	$134.1796	$134.18	$134.20	$134.20
7 purchase totals =	$634.45		$700.6165	$700.62	$700.65	$700.60