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	$151.92	9.215%	$165.9194	$165.92	$165.90	$165.90
Purchase #2	$78.89	6.306%	$83.8648	$83.86	$83.85	$83.90
Purchase #3	$5.94	9.873%	$6.5265	$6.53	$6.55	$6.50
Purchase #4	$90.62	8.721%	$98.523	$98.52	$98.50	$98.50
Purchase #5	$186.83	6.696%	$199.3401	$199.34	$199.35	$199.30
Purchase #6	$109.72	12.781%	$123.7433	$123.74	$123.75	$123.70
Purchase #7	$209.92	12.733%	$236.6491	$236.65	$236.65	$236.60
7 purchase totals =	$833.84		$914.5662	$914.56	$914.55	$914.40