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	$45.25	3.584%	$46.8718	$46.87	$46.85	$46.90
Purchase #2	$152.59	9.617%	$167.2646	$167.26	$167.25	$167.30
Purchase #3	$233.53	6.408%	$248.4946	$248.49	$248.50	$248.50
Purchase #4	$215.40	11.486%	$240.1408	$240.14	$240.15	$240.10
Purchase #5	$92.38	10.312%	$101.9062	$101.91	$101.90	$101.90
Purchase #6	$25.49	8.285%	$27.6018	$27.60	$27.60	$27.60
Purchase #7	$51.95	3.707%	$53.8758	$53.88	$53.90	$53.90
7 purchase totals =	$816.59		$886.1556	$886.15	$886.15	$886.20