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	$96.39	7.704%	$103.8159	$103.82	$103.80	$103.80
Purchase #2	$122.96	6.460%	$130.9032	$130.90	$130.90	$130.90
Purchase #3	$59.27	10.328%	$65.3914	$65.39	$65.40	$65.40
Purchase #4	$204.52	6.849%	$218.5276	$218.53	$218.55	$218.50
Purchase #5	$210.57	3.194%	$217.2956	$217.30	$217.30	$217.30
Purchase #6	$100.26	5.436%	$105.7101	$105.71	$105.70	$105.70
Purchase #7	$247.78	7.505%	$266.3759	$266.38	$266.40	$266.40
7 purchase totals =	$1,041.75		$1,108.0197	$1,108.03	$1,108.05	$1,108.00