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	$59.85	8.870%	$65.1587	$65.16	$65.15	$65.20
Purchase #2	$158.94	5.617%	$167.8677	$167.87	$167.85	$167.90
Purchase #3	$196.56	13.411%	$222.9207	$222.92	$222.90	$222.90
Purchase #4	$186.78	10.390%	$206.1864	$206.19	$206.20	$206.20
Purchase #5	$16.70	8.219%	$18.0726	$18.07	$18.05	$18.10
Purchase #6	$171.33	10.815%	$189.8593	$189.86	$189.85	$189.90
Purchase #7	$244.96	13.438%	$277.8777	$277.88	$277.90	$277.90
7 purchase totals =	$1,035.12		$1,147.9431	$1,147.95	$1,147.90	$1,148.10