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	$176.60	8.114%	$190.9293	$190.93	$190.95	$190.90
Purchase #2	$43.54	4.411%	$45.4605	$45.46	$45.45	$45.50
Purchase #3	$85.41	9.501%	$93.5248	$93.52	$93.50	$93.50
Purchase #4	$88.50	12.505%	$99.5669	$99.57	$99.55	$99.60
Purchase #5	$41.52	7.793%	$44.7557	$44.76	$44.75	$44.80
Purchase #6	$235.98	8.175%	$255.2714	$255.27	$255.25	$255.30
Purchase #7	$118.79	4.807%	$124.5002	$124.50	$124.50	$124.50
7 purchase totals =	$790.34		$854.0088	$854.01	$853.95	$854.10