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	$172.38	10.237%	$190.0265	$190.03	$190.05	$190.00
Purchase #2	$67.52	7.802%	$72.7879	$72.79	$72.80	$72.80
Purchase #3	$88.26	7.482%	$94.8636	$94.86	$94.85	$94.90
Purchase #4	$207.39	4.569%	$216.8656	$216.87	$216.85	$216.90
Purchase #5	$87.89	4.161%	$91.5471	$91.55	$91.55	$91.50
Purchase #6	$186.70	13.266%	$211.4676	$211.47	$211.45	$211.50
Purchase #7	$10.50	4.195%	$10.9405	$10.94	$10.95	$10.90
7 purchase totals =	$820.64		$888.4988	$888.51	$888.50	$888.50