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	$109.56	3.785%	$113.7068	$113.71	$113.70	$113.70
Purchase #2	$167.49	10.672%	$185.3645	$185.36	$185.35	$185.40
Purchase #3	$209.95	5.776%	$222.0767	$222.08	$222.10	$222.10
Purchase #4	$40.26	10.284%	$44.4003	$44.40	$44.40	$44.40
Purchase #5	$123.33	11.850%	$137.9446	$137.94	$137.95	$137.90
Purchase #6	$134.62	3.746%	$139.6629	$139.66	$139.65	$139.70
Purchase #7	$218.75	4.800%	$229.25	$229.25	$229.25	$229.30
7 purchase totals =	$1,003.96		$1,072.4058	$1,072.40	$1,072.40	$1,072.50