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	$41.84	3.419%	$43.2705	$43.27	$43.25	$43.30
Purchase #2	$20.54	5.509%	$21.6715	$21.67	$21.65	$21.70
Purchase #3	$69.73	10.678%	$77.1758	$77.18	$77.20	$77.20
Purchase #4	$175.97	7.275%	$188.7718	$188.77	$188.75	$188.80
Purchase #5	$58.54	11.310%	$65.1609	$65.16	$65.15	$65.20
Purchase #6	$150.51	9.183%	$164.3313	$164.33	$164.35	$164.30
Purchase #7	$47.42	5.553%	$50.0532	$50.05	$50.05	$50.10
7 purchase totals =	$564.55		$610.4350	$610.43	$610.40	$610.60