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	$9.71	5.439%	$10.2381	$10.24	$10.25	$10.20
Purchase #2	$206.76	3.328%	$213.641	$213.64	$213.65	$213.60
Purchase #3	$146.61	13.345%	$166.1751	$166.18	$166.20	$166.20
Purchase #4	$231.95	12.748%	$261.519	$261.52	$261.50	$261.50
Purchase #5	$147.90	13.200%	$167.4228	$167.42	$167.40	$167.40
Purchase #6	$214.78	8.539%	$233.1201	$233.12	$233.10	$233.10
Purchase #7	$238.72	12.592%	$268.7796	$268.78	$268.80	$268.80
7 purchase totals =	$1,196.43		$1,320.8957	$1,320.90	$1,320.90	$1,320.80