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	$131.65	8.650%	$143.0377	$143.04	$143.05	$143.00
Purchase #2	$35.91	6.667%	$38.3041	$38.30	$38.30	$38.30
Purchase #3	$126.36	12.800%	$142.5341	$142.53	$142.55	$142.50
Purchase #4	$199.54	6.112%	$211.7359	$211.74	$211.75	$211.70
Purchase #5	$71.50	11.125%	$79.4544	$79.45	$79.45	$79.50
Purchase #6	$110.43	11.866%	$123.5336	$123.53	$123.55	$123.50
Purchase #7	$136.28	7.581%	$146.6114	$146.61	$146.60	$146.60
7 purchase totals =	$811.67		$885.2112	$885.20	$885.25	$885.10