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	$117.54	8.275%	$127.2664	$127.27	$127.25	$127.30
Purchase #2	$12.65	5.357%	$13.3277	$13.33	$13.35	$13.30
Purchase #3	$63.97	12.363%	$71.8786	$71.88	$71.90	$71.90
Purchase #4	$230.48	6.283%	$244.9611	$244.96	$244.95	$245.00
Purchase #5	$10.56	6.462%	$11.2424	$11.24	$11.25	$11.20
Purchase #6	$197.81	3.551%	$204.8342	$204.83	$204.85	$204.80
Purchase #7	$38.91	10.334%	$42.931	$42.93	$42.95	$42.90
7 purchase totals =	$671.92		$716.4414	$716.44	$716.50	$716.40