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	$169.32	7.235%	$181.5703	$181.57	$181.55	$181.60
Purchase #2	$216.75	7.860%	$233.7866	$233.79	$233.80	$233.80
Purchase #3	$91.91	11.172%	$102.1782	$102.18	$102.20	$102.20
Purchase #4	$80.46	6.495%	$85.6859	$85.69	$85.70	$85.70
Purchase #5	$7.37	5.172%	$7.7512	$7.75	$7.75	$7.80
Purchase #6	$60.56	4.373%	$63.2083	$63.21	$63.20	$63.20
Purchase #7	$88.59	12.193%	$99.3918	$99.39	$99.40	$99.40
7 purchase totals =	$714.96		$773.5723	$773.58	$773.60	$773.70