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	$250.38	4.428%	$261.4668	$261.47	$261.45	$261.50
Purchase #2	$14.82	11.818%	$16.5714	$16.57	$16.55	$16.60
Purchase #3	$78.53	5.490%	$82.8413	$82.84	$82.85	$82.80
Purchase #4	$59.69	13.433%	$67.7082	$67.71	$67.70	$67.70
Purchase #5	$96.97	6.336%	$103.114	$103.11	$103.10	$103.10
Purchase #6	$125.97	11.859%	$140.9088	$140.91	$140.90	$140.90
Purchase #7	$35.91	11.403%	$40.0048	$40.00	$40.00	$40.00
7 purchase totals =	$662.27		$712.6153	$712.61	$712.55	$712.60