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	$145.53	7.429%	$156.3414	$156.34	$156.35	$156.30
Purchase #2	$196.33	12.185%	$220.2528	$220.25	$220.25	$220.30
Purchase #3	$45.67	11.721%	$51.023	$51.02	$51.00	$51.00
Purchase #4	$218.98	11.267%	$243.6525	$243.65	$243.65	$243.70
Purchase #5	$112.73	13.288%	$127.7096	$127.71	$127.70	$127.70
Purchase #6	$86.51	4.523%	$90.4228	$90.42	$90.40	$90.40
Purchase #7	$94.53	11.320%	$105.2308	$105.23	$105.25	$105.20
7 purchase totals =	$900.28		$994.6329	$994.62	$994.60	$994.60