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	$200.66	11.167%	$223.0677	$223.07	$223.05	$223.10
Purchase #2	$214.61	11.758%	$239.8438	$239.84	$239.85	$239.80
Purchase #3	$100.87	10.608%	$111.5703	$111.57	$111.55	$111.60
Purchase #4	$140.90	12.690%	$158.7802	$158.78	$158.80	$158.80
Purchase #5	$229.72	12.331%	$258.0468	$258.05	$258.05	$258.00
Purchase #6	$79.85	7.442%	$85.7924	$85.79	$85.80	$85.80
Purchase #7	$190.86	12.557%	$214.8263	$214.83	$214.85	$214.80
7 purchase totals =	$1,157.47		$1,291.9275	$1,291.93	$1,291.95	$1,291.90