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	$67.58	8.412%	$73.2648	$73.26	$73.25	$73.30
Purchase #2	$196.97	4.232%	$205.3058	$205.31	$205.30	$205.30
Purchase #3	$92.92	10.128%	$102.3309	$102.33	$102.35	$102.30
Purchase #4	$183.78	3.549%	$190.3024	$190.30	$190.30	$190.30
Purchase #5	$10.55	12.872%	$11.908	$11.91	$11.90	$11.90
Purchase #6	$110.40	7.312%	$118.4724	$118.47	$118.45	$118.50
Purchase #7	$115.53	11.301%	$128.586	$128.59	$128.60	$128.60
7 purchase totals =	$777.73		$830.1703	$830.17	$830.15	$830.20