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	$169.67	11.152%	$188.5916	$188.59	$188.60	$188.60
Purchase #2	$135.51	8.151%	$146.5554	$146.56	$146.55	$146.60
Purchase #3	$89.50	12.607%	$100.7833	$100.78	$100.80	$100.80
Purchase #4	$173.63	3.620%	$179.9154	$179.92	$179.90	$179.90
Purchase #5	$102.63	7.196%	$110.0153	$110.02	$110.00	$110.00
Purchase #6	$209.90	12.622%	$236.3936	$236.39	$236.40	$236.40
Purchase #7	$248.44	7.314%	$266.6109	$266.61	$266.60	$266.60
7 purchase totals =	$1,129.28		$1,228.8655	$1,228.87	$1,228.85	$1,228.90