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	$92.91	7.419%	$99.803	$99.80	$99.80	$99.80
Purchase #2	$124.74	9.711%	$136.8535	$136.85	$136.85	$136.90
Purchase #3	$100.72	7.484%	$108.2579	$108.26	$108.25	$108.30
Purchase #4	$209.97	7.463%	$225.6401	$225.64	$225.65	$225.60
Purchase #5	$128.70	13.105%	$145.5661	$145.57	$145.55	$145.60
Purchase #6	$172.32	9.345%	$188.4233	$188.42	$188.40	$188.40
Purchase #7	$98.98	7.845%	$106.745	$106.75	$106.75	$106.70
7 purchase totals =	$928.34		$1,011.2889	$1,011.29	$1,011.25	$1,011.30