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	$137.62	5.862%	$145.6873	$145.69	$145.70	$145.70
Purchase #2	$173.87	13.166%	$196.7617	$196.76	$196.75	$196.80
Purchase #3	$230.70	13.688%	$262.2782	$262.28	$262.30	$262.30
Purchase #4	$150.42	8.320%	$162.9349	$162.93	$162.95	$162.90
Purchase #5	$137.68	11.389%	$153.3604	$153.36	$153.35	$153.40
Purchase #6	$53.38	6.576%	$56.8903	$56.89	$56.90	$56.90
Purchase #7	$110.68	9.215%	$120.8792	$120.88	$120.90	$120.90
7 purchase totals =	$994.35		$1,098.7920	$1,098.79	$1,098.85	$1,098.90