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	$142.99	4.857%	$149.935	$149.94	$149.95	$149.90
Purchase #2	$64.78	13.487%	$73.5169	$73.52	$73.50	$73.50
Purchase #3	$114.86	5.443%	$121.1118	$121.11	$121.10	$121.10
Purchase #4	$71.96	9.426%	$78.7429	$78.74	$78.75	$78.70
Purchase #5	$101.53	3.595%	$105.18	$105.18	$105.20	$105.20
Purchase #6	$178.51	11.632%	$199.2743	$199.27	$199.25	$199.30
Purchase #7	$149.75	13.162%	$169.4601	$169.46	$169.45	$169.50
7 purchase totals =	$824.38		$897.2210	$897.22	$897.20	$897.20