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	$205.47	8.670%	$223.2842	$223.28	$223.30	$223.30
Purchase #2	$215.97	3.126%	$222.7212	$222.72	$222.70	$222.70
Purchase #3	$59.84	9.231%	$65.3638	$65.36	$65.35	$65.40
Purchase #4	$195.88	6.251%	$208.1245	$208.12	$208.10	$208.10
Purchase #5	$213.34	4.166%	$222.2277	$222.23	$222.25	$222.20
Purchase #6	$60.39	6.632%	$64.3951	$64.40	$64.40	$64.40
Purchase #7	$98.46	6.244%	$104.6078	$104.61	$104.60	$104.60
7 purchase totals =	$1,049.35		$1,110.7243	$1,110.72	$1,110.70	$1,110.70