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	$139.75	4.437%	$145.9507	$145.95	$145.95	$146.00
Purchase #2	$64.98	11.842%	$72.6749	$72.67	$72.65	$72.70
Purchase #3	$83.27	3.848%	$86.4742	$86.47	$86.45	$86.50
Purchase #4	$80.87	11.627%	$90.2728	$90.27	$90.25	$90.30
Purchase #5	$249.90	12.577%	$281.3299	$281.33	$281.35	$281.30
Purchase #6	$192.45	7.317%	$206.5316	$206.53	$206.55	$206.50
Purchase #7	$241.83	6.303%	$257.0725	$257.07	$257.05	$257.10
7 purchase totals =	$1,053.05		$1,140.3066	$1,140.29	$1,140.25	$1,140.40