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	$105.57	8.294%	$114.326	$114.33	$114.35	$114.30
Purchase #2	$193.83	11.170%	$215.4808	$215.48	$215.50	$215.50
Purchase #3	$134.26	4.133%	$139.809	$139.81	$139.80	$139.80
Purchase #4	$47.86	3.713%	$49.637	$49.64	$49.65	$49.60
Purchase #5	$194.57	10.248%	$214.5095	$214.51	$214.50	$214.50
Purchase #6	$218.50	6.410%	$232.5059	$232.51	$232.50	$232.50
Purchase #7	$155.87	6.164%	$165.4778	$165.48	$165.50	$165.50
7 purchase totals =	$1,050.46		$1,131.7460	$1,131.76	$1,131.80	$1,131.70