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	$109.67	7.704%	$118.119	$118.12	$118.10	$118.10
Purchase #2	$206.80	12.480%	$232.6086	$232.61	$232.60	$232.60
Purchase #3	$235.69	9.824%	$258.8442	$258.84	$258.85	$258.80
Purchase #4	$246.50	3.233%	$254.4693	$254.47	$254.45	$254.50
Purchase #5	$68.58	5.625%	$72.4376	$72.44	$72.45	$72.40
Purchase #6	$212.36	13.442%	$240.9054	$240.91	$240.90	$240.90
Purchase #7	$182.65	7.613%	$196.5551	$196.56	$196.55	$196.60
7 purchase totals =	$1,262.25		$1,373.9392	$1,373.95	$1,373.90	$1,373.90