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	$100.77	8.855%	$109.6932	$109.69	$109.70	$109.70
Purchase #2	$85.86	5.419%	$90.5128	$90.51	$90.50	$90.50
Purchase #3	$84.62	10.483%	$93.4907	$93.49	$93.50	$93.50
Purchase #4	$75.77	7.476%	$81.4346	$81.43	$81.45	$81.40
Purchase #5	$29.47	6.685%	$31.4401	$31.44	$31.45	$31.40
Purchase #6	$147.45	7.689%	$158.7874	$158.79	$158.80	$158.80
Purchase #7	$167.31	8.761%	$181.968	$181.97	$181.95	$182.00
7 purchase totals =	$691.25		$747.3268	$747.32	$747.35	$747.30