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	$95.28	5.572%	$100.589	$100.59	$100.60	$100.60
Purchase #2	$157.31	13.414%	$178.4116	$178.41	$178.40	$178.40
Purchase #3	$172.31	6.433%	$183.3947	$183.39	$183.40	$183.40
Purchase #4	$171.27	10.366%	$189.0238	$189.02	$189.00	$189.00
Purchase #5	$160.90	4.711%	$168.48	$168.48	$168.50	$168.50
Purchase #6	$248.73	9.568%	$272.5285	$272.53	$272.55	$272.50
Purchase #7	$100.56	4.126%	$104.7091	$104.71	$104.70	$104.70
7 purchase totals =	$1,106.36		$1,197.1367	$1,197.13	$1,197.15	$1,197.10