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	$187.81	10.392%	$207.3272	$207.33	$207.35	$207.30
Purchase #2	$82.38	6.817%	$87.9958	$88.00	$88.00	$88.00
Purchase #3	$21.97	3.578%	$22.7561	$22.76	$22.75	$22.80
Purchase #4	$72.31	8.688%	$78.5923	$78.59	$78.60	$78.60
Purchase #5	$74.82	4.464%	$78.16	$78.16	$78.15	$78.20
Purchase #6	$70.25	11.868%	$78.5873	$78.59	$78.60	$78.60
Purchase #7	$75.65	12.381%	$85.0162	$85.02	$85.00	$85.00
7 purchase totals =	$585.19		$638.4349	$638.45	$638.45	$638.50