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	$127.39	9.139%	$139.0322	$139.03	$139.05	$139.00
Purchase #2	$210.40	6.404%	$223.874	$223.87	$223.85	$223.90
Purchase #3	$201.74	7.228%	$216.3218	$216.32	$216.30	$216.30
Purchase #4	$89.81	7.242%	$96.314	$96.31	$96.30	$96.30
Purchase #5	$69.87	10.576%	$77.2595	$77.26	$77.25	$77.30
Purchase #6	$44.94	7.178%	$48.1658	$48.17	$48.15	$48.20
Purchase #7	$138.31	8.496%	$150.0608	$150.06	$150.05	$150.10
7 purchase totals =	$882.46		$951.0281	$951.02	$950.95	$951.10