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	$204.56	4.181%	$213.1127	$213.11	$213.10	$213.10
Purchase #2	$17.90	5.346%	$18.8569	$18.86	$18.85	$18.90
Purchase #3	$179.73	4.467%	$187.7585	$187.76	$187.75	$187.80
Purchase #4	$100.43	9.123%	$109.5922	$109.59	$109.60	$109.60
Purchase #5	$193.68	3.175%	$199.8293	$199.83	$199.85	$199.80
Purchase #6	$218.76	4.455%	$228.5058	$228.51	$228.50	$228.50
Purchase #7	$66.28	5.410%	$69.8657	$69.87	$69.85	$69.90
7 purchase totals =	$981.34		$1,027.5211	$1,027.53	$1,027.50	$1,027.60