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	$50.32	8.642%	$54.6687	$54.67	$54.65	$54.70
Purchase #2	$248.85	11.427%	$277.2861	$277.29	$277.30	$277.30
Purchase #3	$179.31	11.684%	$200.2606	$200.26	$200.25	$200.30
Purchase #4	$213.56	6.635%	$227.7297	$227.73	$227.75	$227.70
Purchase #5	$39.96	10.836%	$44.2901	$44.29	$44.30	$44.30
Purchase #6	$82.66	3.768%	$85.7746	$85.77	$85.75	$85.80
Purchase #7	$180.67	5.716%	$190.9971	$191.00	$191.00	$191.00
7 purchase totals =	$995.33		$1,081.0069	$1,081.01	$1,081.00	$1,081.10