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	$78.64	9.512%	$86.1202	$86.12	$86.10	$86.10
Purchase #2	$8.97	13.688%	$10.1978	$10.20	$10.20	$10.20
Purchase #3	$228.34	5.652%	$241.2458	$241.25	$241.25	$241.20
Purchase #4	$233.29	4.214%	$243.1208	$243.12	$243.10	$243.10
Purchase #5	$109.94	12.379%	$123.5495	$123.55	$123.55	$123.50
Purchase #6	$142.51	3.491%	$147.485	$147.49	$147.50	$147.50
Purchase #7	$215.63	6.464%	$229.5683	$229.57	$229.55	$229.60
7 purchase totals =	$1,017.32		$1,081.2874	$1,081.30	$1,081.25	$1,081.20