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	$108.90	7.740%	$117.3289	$117.33	$117.35	$117.30
Purchase #2	$37.54	4.836%	$39.3554	$39.36	$39.35	$39.40
Purchase #3	$247.71	4.242%	$258.2179	$258.22	$258.20	$258.20
Purchase #4	$69.77	4.446%	$72.872	$72.87	$72.85	$72.90
Purchase #5	$120.33	6.233%	$127.8302	$127.83	$127.85	$127.80
Purchase #6	$133.99	3.365%	$138.4988	$138.50	$138.50	$138.50
Purchase #7	$208.65	7.465%	$224.2257	$224.23	$224.25	$224.20
7 purchase totals =	$926.89		$978.3289	$978.34	$978.35	$978.30