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	$105.51	10.750%	$116.8523	$116.85	$116.85	$116.90
Purchase #2	$52.49	4.473%	$54.8379	$54.84	$54.85	$54.80
Purchase #3	$128.27	10.436%	$141.6563	$141.66	$141.65	$141.70
Purchase #4	$106.34	7.483%	$114.2974	$114.30	$114.30	$114.30
Purchase #5	$72.90	13.676%	$82.8698	$82.87	$82.85	$82.90
Purchase #6	$94.78	5.686%	$100.1692	$100.17	$100.15	$100.20
Purchase #7	$58.91	3.417%	$60.923	$60.92	$60.90	$60.90
7 purchase totals =	$619.20		$671.6059	$671.61	$671.55	$671.70