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	$10.28	11.845%	$11.4977	$11.50	$11.50	$11.50
Purchase #2	$160.63	12.767%	$181.1376	$181.14	$181.15	$181.10
Purchase #3	$53.29	12.212%	$59.7978	$59.80	$59.80	$59.80
Purchase #4	$110.44	5.567%	$116.5882	$116.59	$116.60	$116.60
Purchase #5	$169.84	8.176%	$183.7261	$183.73	$183.75	$183.70
Purchase #6	$181.98	5.114%	$191.2865	$191.29	$191.30	$191.30
Purchase #7	$21.27	5.431%	$22.4252	$22.43	$22.45	$22.40
7 purchase totals =	$707.73		$766.4591	$766.48	$766.55	$766.40