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	$105.51	8.415%	$114.3887	$114.39	$114.40	$114.40
Purchase #2	$131.73	11.377%	$146.7169	$146.72	$146.70	$146.70
Purchase #3	$24.94	11.398%	$27.7827	$27.78	$27.80	$27.80
Purchase #4	$160.90	4.339%	$167.8815	$167.88	$167.90	$167.90
Purchase #5	$156.33	5.790%	$165.3815	$165.38	$165.40	$165.40
Purchase #6	$149.67	5.285%	$157.5801	$157.58	$157.60	$157.60
Purchase #7	$42.83	12.658%	$48.2514	$48.25	$48.25	$48.30
7 purchase totals =	$771.91		$827.9828	$827.98	$828.05	$828.10