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	$91.74	10.574%	$101.4406	$101.44	$101.45	$101.40
Purchase #2	$152.70	5.368%	$160.8969	$160.90	$160.90	$160.90
Purchase #3	$115.55	7.191%	$123.8592	$123.86	$123.85	$123.90
Purchase #4	$244.69	7.180%	$262.2587	$262.26	$262.25	$262.30
Purchase #5	$88.63	11.160%	$98.5211	$98.52	$98.50	$98.50
Purchase #6	$76.39	5.311%	$80.4471	$80.45	$80.45	$80.40
Purchase #7	$36.66	10.670%	$40.5716	$40.57	$40.55	$40.60
7 purchase totals =	$806.36		$867.9952	$868.00	$867.95	$868.00