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	$248.82	5.772%	$263.1819	$263.18	$263.20	$263.20
Purchase #2	$179.51	9.540%	$196.6353	$196.64	$196.65	$196.60
Purchase #3	$139.33	9.107%	$152.0188	$152.02	$152.00	$152.00
Purchase #4	$237.98	9.331%	$260.1859	$260.19	$260.20	$260.20
Purchase #5	$57.53	8.339%	$62.3274	$62.33	$62.35	$62.30
Purchase #6	$53.53	4.197%	$55.7767	$55.78	$55.80	$55.80
Purchase #7	$54.64	3.643%	$56.6305	$56.63	$56.65	$56.60
7 purchase totals =	$971.34		$1,046.7565	$1,046.77	$1,046.85	$1,046.70