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	$139.27	13.711%	$158.3653	$158.37	$158.35	$158.40
Purchase #2	$41.98	9.554%	$45.9908	$45.99	$46.00	$46.00
Purchase #3	$145.44	3.598%	$150.6729	$150.67	$150.65	$150.70
Purchase #4	$80.81	10.190%	$89.0445	$89.04	$89.05	$89.00
Purchase #5	$176.57	5.749%	$186.721	$186.72	$186.70	$186.70
Purchase #6	$139.59	4.559%	$145.9539	$145.95	$145.95	$146.00
Purchase #7	$218.44	10.217%	$240.758	$240.76	$240.75	$240.80
7 purchase totals =	$942.10		$1,017.5064	$1,017.50	$1,017.45	$1,017.60