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	$108.78	13.196%	$123.1346	$123.13	$123.15	$123.10
Purchase #2	$54.34	13.136%	$61.4781	$61.48	$61.50	$61.50
Purchase #3	$126.31	5.284%	$132.9842	$132.98	$133.00	$133.00
Purchase #4	$237.35	4.811%	$248.7689	$248.77	$248.75	$248.80
Purchase #5	$47.33	12.872%	$53.4223	$53.42	$53.40	$53.40
Purchase #6	$199.89	12.313%	$224.5025	$224.50	$224.50	$224.50
Purchase #7	$114.27	8.291%	$123.7441	$123.74	$123.75	$123.70
7 purchase totals =	$888.27		$968.0347	$968.02	$968.05	$968.00