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	$42.46	12.378%	$47.7157	$47.72	$47.70	$47.70
Purchase #2	$85.27	7.156%	$91.3719	$91.37	$91.35	$91.40
Purchase #3	$97.73	8.221%	$105.7644	$105.76	$105.75	$105.80
Purchase #4	$173.32	9.341%	$189.5098	$189.51	$189.50	$189.50
Purchase #5	$35.67	7.303%	$38.275	$38.28	$38.30	$38.30
Purchase #6	$200.65	7.181%	$215.0587	$215.06	$215.05	$215.10
Purchase #7	$231.44	11.682%	$258.4768	$258.48	$258.50	$258.50
7 purchase totals =	$866.54		$946.1723	$946.18	$946.15	$946.30