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	$146.81	5.264%	$154.5381	$154.54	$154.55	$154.50
Purchase #2	$181.59	4.293%	$189.3857	$189.39	$189.40	$189.40
Purchase #3	$144.51	5.197%	$152.0202	$152.02	$152.00	$152.00
Purchase #4	$53.26	12.240%	$59.779	$59.78	$59.80	$59.80
Purchase #5	$248.42	12.581%	$279.6737	$279.67	$279.65	$279.70
Purchase #6	$122.93	11.547%	$137.1247	$137.12	$137.10	$137.10
Purchase #7	$166.86	4.862%	$174.9727	$174.97	$174.95	$175.00
7 purchase totals =	$1,064.38		$1,147.4941	$1,147.49	$1,147.45	$1,147.50