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	$89.52	13.740%	$101.82	$101.82	$101.80	$101.80
Purchase #2	$24.74	13.372%	$28.0482	$28.05	$28.05	$28.00
Purchase #3	$185.80	5.551%	$196.1138	$196.11	$196.10	$196.10
Purchase #4	$25.35	7.452%	$27.2391	$27.24	$27.25	$27.20
Purchase #5	$143.90	9.861%	$158.09	$158.09	$158.10	$158.10
Purchase #6	$73.84	5.179%	$77.6642	$77.66	$77.65	$77.70
Purchase #7	$79.81	13.567%	$90.6378	$90.64	$90.65	$90.60
7 purchase totals =	$622.96		$679.6131	$679.61	$679.60	$679.50