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	$185.59	12.594%	$208.9632	$208.96	$208.95	$209.00
Purchase #2	$182.95	12.385%	$205.6084	$205.61	$205.60	$205.60
Purchase #3	$244.78	10.858%	$271.3582	$271.36	$271.35	$271.40
Purchase #4	$187.68	6.166%	$199.2523	$199.25	$199.25	$199.30
Purchase #5	$80.37	3.121%	$82.8783	$82.88	$82.90	$82.90
Purchase #6	$100.57	10.476%	$111.1057	$111.11	$111.10	$111.10
Purchase #7	$227.59	6.872%	$243.23	$243.23	$243.25	$243.20
7 purchase totals =	$1,209.53		$1,322.3961	$1,322.40	$1,322.40	$1,322.50