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	$203.32	9.421%	$222.4748	$222.47	$222.45	$222.50
Purchase #2	$6.91	10.124%	$7.6096	$7.61	$7.60	$7.60
Purchase #3	$216.31	5.676%	$228.5878	$228.59	$228.60	$228.60
Purchase #4	$79.41	4.182%	$82.7309	$82.73	$82.75	$82.70
Purchase #5	$139.36	9.816%	$153.0396	$153.04	$153.05	$153.00
Purchase #6	$14.33	10.702%	$15.8636	$15.86	$15.85	$15.90
Purchase #7	$61.89	4.146%	$64.456	$64.46	$64.45	$64.50
7 purchase totals =	$721.53		$774.7623	$774.76	$774.75	$774.80