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	$196.62	11.785%	$219.7917	$219.79	$219.80	$219.80
Purchase #2	$104.75	6.824%	$111.8981	$111.90	$111.90	$111.90
Purchase #3	$210.27	11.144%	$233.7025	$233.70	$233.70	$233.70
Purchase #4	$136.26	10.405%	$150.4379	$150.44	$150.45	$150.40
Purchase #5	$237.77	8.598%	$258.2135	$258.21	$258.20	$258.20
Purchase #6	$151.33	11.339%	$168.4893	$168.49	$168.50	$168.50
Purchase #7	$60.33	10.693%	$66.7811	$66.78	$66.80	$66.80
7 purchase totals =	$1,097.33		$1,209.3141	$1,209.31	$1,209.35	$1,209.30