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	$162.90	10.211%	$179.5337	$179.53	$179.55	$179.50
Purchase #2	$32.68	8.700%	$35.5232	$35.52	$35.50	$35.50
Purchase #3	$159.26	8.215%	$172.3432	$172.34	$172.35	$172.30
Purchase #4	$59.70	10.793%	$66.1434	$66.14	$66.15	$66.10
Purchase #5	$80.81	12.377%	$90.8119	$90.81	$90.80	$90.80
Purchase #6	$221.78	10.681%	$245.4683	$245.47	$245.45	$245.50
Purchase #7	$250.61	8.198%	$271.155	$271.16	$271.15	$271.20
7 purchase totals =	$967.74		$1,060.9787	$1,060.97	$1,060.95	$1,060.90