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	$30.98	12.806%	$34.9473	$34.95	$34.95	$34.90
Purchase #2	$136.79	4.810%	$143.3696	$143.37	$143.35	$143.40
Purchase #3	$174.74	12.155%	$195.9796	$195.98	$196.00	$196.00
Purchase #4	$62.45	12.621%	$70.3318	$70.33	$70.35	$70.30
Purchase #5	$120.38	3.687%	$124.8184	$124.82	$124.80	$124.80
Purchase #6	$150.76	11.110%	$167.5094	$167.51	$167.50	$167.50
Purchase #7	$243.56	8.834%	$265.0761	$265.08	$265.10	$265.10
7 purchase totals =	$919.66		$1,002.0322	$1,002.04	$1,002.05	$1,002.00