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	$147.56	6.307%	$156.8666	$156.87	$156.85	$156.90
Purchase #2	$23.94	6.473%	$25.4896	$25.49	$25.50	$25.50
Purchase #3	$31.78	3.727%	$32.9644	$32.96	$32.95	$33.00
Purchase #4	$198.50	10.125%	$218.5981	$218.60	$218.60	$218.60
Purchase #5	$179.35	9.469%	$196.3327	$196.33	$196.35	$196.30
Purchase #6	$70.75	5.303%	$74.5019	$74.50	$74.50	$74.50
Purchase #7	$239.66	6.155%	$254.4111	$254.41	$254.40	$254.40
7 purchase totals =	$891.54		$959.1644	$959.16	$959.15	$959.20