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	$42.91	6.460%	$45.682	$45.68	$45.70	$45.70
Purchase #2	$89.27	7.789%	$96.2232	$96.22	$96.20	$96.20
Purchase #3	$140.80	3.517%	$145.7519	$145.75	$145.75	$145.80
Purchase #4	$240.30	12.549%	$270.4552	$270.46	$270.45	$270.50
Purchase #5	$54.27	5.812%	$57.4242	$57.42	$57.40	$57.40
Purchase #6	$144.55	11.397%	$161.0244	$161.02	$161.00	$161.00
Purchase #7	$216.68	3.349%	$223.9366	$223.94	$223.95	$223.90
7 purchase totals =	$928.78		$1,000.4975	$1,000.49	$1,000.45	$1,000.50