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	$92.64	8.841%	$100.8303	$100.83	$100.85	$100.80
Purchase #2	$45.33	12.259%	$50.887	$50.89	$50.90	$50.90
Purchase #3	$219.73	9.483%	$240.567	$240.57	$240.55	$240.60
Purchase #4	$201.82	8.869%	$219.7194	$219.72	$219.70	$219.70
Purchase #5	$222.27	10.352%	$245.2794	$245.28	$245.30	$245.30
Purchase #6	$72.83	9.591%	$79.8151	$79.82	$79.80	$79.80
Purchase #7	$244.42	11.200%	$271.795	$271.80	$271.80	$271.80
7 purchase totals =	$1,099.04		$1,208.8932	$1,208.91	$1,208.90	$1,208.90