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	$99.41	10.358%	$109.7069	$109.71	$109.70	$109.70
Purchase #2	$94.65	5.288%	$99.6551	$99.66	$99.65	$99.70
Purchase #3	$55.98	13.201%	$63.3699	$63.37	$63.35	$63.40
Purchase #4	$88.53	4.531%	$92.5413	$92.54	$92.55	$92.50
Purchase #5	$169.46	13.211%	$191.8474	$191.85	$191.85	$191.80
Purchase #6	$185.58	13.152%	$209.9875	$209.99	$210.00	$210.00
Purchase #7	$201.31	4.209%	$209.7831	$209.78	$209.80	$209.80
7 purchase totals =	$894.92		$976.8912	$976.90	$976.90	$976.90