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	$160.73	11.516%	$179.2397	$179.24	$179.25	$179.20
Purchase #2	$170.35	4.840%	$178.5949	$178.59	$178.60	$178.60
Purchase #3	$123.79	10.706%	$137.043	$137.04	$137.05	$137.00
Purchase #4	$93.62	12.601%	$105.4171	$105.42	$105.40	$105.40
Purchase #5	$206.70	10.774%	$228.9699	$228.97	$228.95	$229.00
Purchase #6	$181.45	13.452%	$205.8587	$205.86	$205.85	$205.90
Purchase #7	$99.86	11.447%	$111.291	$111.29	$111.30	$111.30
7 purchase totals =	$1,036.50		$1,146.4143	$1,146.41	$1,146.40	$1,146.40