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	$172.62	12.349%	$193.9368	$193.94	$193.95	$193.90
Purchase #2	$84.38	8.213%	$91.3101	$91.31	$91.30	$91.30
Purchase #3	$179.45	6.266%	$190.6943	$190.69	$190.70	$190.70
Purchase #4	$72.72	13.520%	$82.5517	$82.55	$82.55	$82.60
Purchase #5	$222.46	4.744%	$233.0135	$233.01	$233.00	$233.00
Purchase #6	$104.97	6.202%	$111.4802	$111.48	$111.50	$111.50
Purchase #7	$24.79	5.316%	$26.1078	$26.11	$26.10	$26.10
7 purchase totals =	$861.39		$929.0944	$929.09	$929.10	$929.10