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	$124.27	8.519%	$134.8566	$134.86	$134.85	$134.90
Purchase #2	$198.77	5.502%	$209.7063	$209.71	$209.70	$209.70
Purchase #3	$120.79	10.344%	$133.2845	$133.28	$133.30	$133.30
Purchase #4	$134.77	8.262%	$145.9047	$145.90	$145.90	$145.90
Purchase #5	$55.76	12.656%	$62.817	$62.82	$62.80	$62.80
Purchase #6	$64.74	12.337%	$72.727	$72.73	$72.75	$72.70
Purchase #7	$93.64	7.566%	$100.7248	$100.72	$100.70	$100.70
7 purchase totals =	$792.74		$860.0209	$860.02	$860.00	$860.00