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	$250.43	12.562%	$281.889	$281.89	$281.90	$281.90
Purchase #2	$59.45	7.825%	$64.102	$64.10	$64.10	$64.10
Purchase #3	$213.52	4.254%	$222.6031	$222.60	$222.60	$222.60
Purchase #4	$39.70	12.264%	$44.5688	$44.57	$44.55	$44.60
Purchase #5	$142.71	11.712%	$159.4242	$159.42	$159.40	$159.40
Purchase #6	$192.97	6.543%	$205.596	$205.60	$205.60	$205.60
Purchase #7	$232.77	7.488%	$250.1998	$250.20	$250.20	$250.20
7 purchase totals =	$1,131.55		$1,228.3829	$1,228.38	$1,228.35	$1,228.40