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	$130.35	9.432%	$142.6446	$142.64	$142.65	$142.60
Purchase #2	$48.29	5.306%	$50.8523	$50.85	$50.85	$50.90
Purchase #3	$32.72	3.581%	$33.8917	$33.89	$33.90	$33.90
Purchase #4	$109.42	4.254%	$114.0747	$114.07	$114.05	$114.10
Purchase #5	$161.66	4.279%	$168.5774	$168.58	$168.60	$168.60
Purchase #6	$46.92	9.333%	$51.299	$51.30	$51.30	$51.30
Purchase #7	$81.33	4.738%	$85.1834	$85.18	$85.20	$85.20
7 purchase totals =	$610.69		$646.5231	$646.51	$646.55	$646.60