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	$195.69	12.256%	$219.6738	$219.67	$219.65	$219.70
Purchase #2	$28.73	7.823%	$30.9775	$30.98	$31.00	$31.00
Purchase #3	$193.30	8.540%	$209.8078	$209.81	$209.80	$209.80
Purchase #4	$144.89	9.356%	$158.4459	$158.45	$158.45	$158.40
Purchase #5	$105.89	8.342%	$114.7233	$114.72	$114.70	$114.70
Purchase #6	$61.52	3.766%	$63.8368	$63.84	$63.85	$63.80
Purchase #7	$198.38	12.601%	$223.3779	$223.38	$223.40	$223.40
7 purchase totals =	$928.40		$1,020.8430	$1,020.85	$1,020.85	$1,020.80