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	$90.55	8.708%	$98.4351	$98.44	$98.45	$98.40
Purchase #2	$86.26	8.476%	$93.5714	$93.57	$93.55	$93.60
Purchase #3	$84.85	10.837%	$94.0452	$94.05	$94.05	$94.00
Purchase #4	$80.94	5.655%	$85.5172	$85.52	$85.50	$85.50
Purchase #5	$248.35	13.186%	$281.0974	$281.10	$281.10	$281.10
Purchase #6	$99.51	12.561%	$112.0095	$112.01	$112.00	$112.00
Purchase #7	$80.81	11.231%	$89.8858	$89.89	$89.90	$89.90
7 purchase totals =	$771.27		$854.5616	$854.58	$854.55	$854.50