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	$166.54	8.443%	$180.601	$180.60	$180.60	$180.60
Purchase #2	$99.47	8.433%	$107.8583	$107.86	$107.85	$107.90
Purchase #3	$135.57	5.116%	$142.5058	$142.51	$142.50	$142.50
Purchase #4	$217.83	12.826%	$245.7689	$245.77	$245.75	$245.80
Purchase #5	$104.73	6.558%	$111.5982	$111.60	$111.60	$111.60
Purchase #6	$34.96	5.502%	$36.8835	$36.88	$36.90	$36.90
Purchase #7	$106.77	5.673%	$112.8271	$112.83	$112.85	$112.80
7 purchase totals =	$865.87		$938.0428	$938.05	$938.05	$938.10