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	$85.25	9.690%	$93.5107	$93.51	$93.50	$93.50
Purchase #2	$237.88	4.361%	$248.2539	$248.25	$248.25	$248.30
Purchase #3	$146.67	10.575%	$162.1804	$162.18	$162.20	$162.20
Purchase #4	$100.45	5.163%	$105.6362	$105.64	$105.65	$105.60
Purchase #5	$245.53	5.778%	$259.7167	$259.72	$259.70	$259.70
Purchase #6	$143.49	7.850%	$154.754	$154.75	$154.75	$154.80
Purchase #7	$89.74	12.357%	$100.8292	$100.83	$100.85	$100.80
7 purchase totals =	$1,049.01		$1,124.8811	$1,124.88	$1,124.90	$1,124.90