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	$59.90	5.463%	$63.1723	$63.17	$63.15	$63.20
Purchase #2	$37.41	6.611%	$39.8832	$39.88	$39.90	$39.90
Purchase #3	$228.94	7.192%	$245.4054	$245.41	$245.40	$245.40
Purchase #4	$124.56	11.689%	$139.1198	$139.12	$139.10	$139.10
Purchase #5	$151.59	5.658%	$160.167	$160.17	$160.15	$160.20
Purchase #6	$221.39	13.300%	$250.8349	$250.83	$250.85	$250.80
Purchase #7	$73.45	13.811%	$83.5942	$83.59	$83.60	$83.60
7 purchase totals =	$897.24		$982.1768	$982.17	$982.15	$982.20