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	$116.79	12.388%	$131.2579	$131.26	$131.25	$131.30
Purchase #2	$195.73	5.515%	$206.5245	$206.52	$206.50	$206.50
Purchase #3	$6.62	11.387%	$7.3738	$7.37	$7.35	$7.40
Purchase #4	$245.96	5.383%	$259.2	$259.20	$259.20	$259.20
Purchase #5	$242.70	5.420%	$255.8543	$255.85	$255.85	$255.90
Purchase #6	$205.28	9.515%	$224.8124	$224.81	$224.80	$224.80
Purchase #7	$37.36	13.250%	$42.3102	$42.31	$42.30	$42.30
7 purchase totals =	$1,050.44		$1,127.3331	$1,127.32	$1,127.25	$1,127.40