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	$43.70	4.327%	$45.5909	$45.59	$45.60	$45.60
Purchase #2	$81.96	4.557%	$85.6949	$85.69	$85.70	$85.70
Purchase #3	$146.31	11.245%	$162.7626	$162.76	$162.75	$162.80
Purchase #4	$205.57	10.788%	$227.7469	$227.75	$227.75	$227.70
Purchase #5	$250.49	11.503%	$279.3039	$279.30	$279.30	$279.30
Purchase #6	$206.45	4.257%	$215.2386	$215.24	$215.25	$215.20
Purchase #7	$124.48	11.834%	$139.211	$139.21	$139.20	$139.20
7 purchase totals =	$1,058.96		$1,155.5488	$1,155.54	$1,155.55	$1,155.50