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	$151.93	9.377%	$166.1765	$166.18	$166.20	$166.20
Purchase #2	$153.90	5.689%	$162.6554	$162.66	$162.65	$162.70
Purchase #3	$155.40	10.385%	$171.5383	$171.54	$171.55	$171.50
Purchase #4	$190.53	8.443%	$206.6164	$206.62	$206.60	$206.60
Purchase #5	$89.86	13.430%	$101.9282	$101.93	$101.95	$101.90
Purchase #6	$91.28	3.525%	$94.4976	$94.50	$94.50	$94.50
Purchase #7	$28.79	11.510%	$32.1037	$32.10	$32.10	$32.10
7 purchase totals =	$861.69		$935.5161	$935.53	$935.55	$935.50