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	$206.82	13.842%	$235.448	$235.45	$235.45	$235.40
Purchase #2	$248.44	5.591%	$262.3303	$262.33	$262.35	$262.30
Purchase #3	$76.34	9.628%	$83.69	$83.69	$83.70	$83.70
Purchase #4	$78.79	6.502%	$83.9129	$83.91	$83.90	$83.90
Purchase #5	$115.84	6.615%	$123.5028	$123.50	$123.50	$123.50
Purchase #6	$53.60	11.200%	$59.6032	$59.60	$59.60	$59.60
Purchase #7	$16.48	3.756%	$17.099	$17.10	$17.10	$17.10
7 purchase totals =	$796.31		$865.5862	$865.58	$865.60	$865.50