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	$210.26	13.297%	$238.2183	$238.22	$238.20	$238.20
Purchase #2	$86.42	4.572%	$90.3711	$90.37	$90.35	$90.40
Purchase #3	$91.46	13.776%	$104.0595	$104.06	$104.05	$104.10
Purchase #4	$121.36	8.193%	$131.303	$131.30	$131.30	$131.30
Purchase #5	$118.39	11.601%	$132.1244	$132.12	$132.10	$132.10
Purchase #6	$10.88	9.543%	$11.9183	$11.92	$11.90	$11.90
Purchase #7	$180.66	8.627%	$196.2455	$196.25	$196.25	$196.20
7 purchase totals =	$819.43		$904.2401	$904.24	$904.15	$904.20