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	$76.25	3.314%	$78.7769	$78.78	$78.80	$78.80
Purchase #2	$17.39	10.628%	$19.2382	$19.24	$19.25	$19.20
Purchase #3	$118.71	12.242%	$133.2425	$133.24	$133.25	$133.20
Purchase #4	$59.81	6.351%	$63.6085	$63.61	$63.60	$63.60
Purchase #5	$118.86	10.482%	$131.3189	$131.32	$131.30	$131.30
Purchase #6	$33.91	6.752%	$36.1996	$36.20	$36.20	$36.20
Purchase #7	$20.53	11.355%	$22.8612	$22.86	$22.85	$22.90
7 purchase totals =	$445.46		$485.2458	$485.25	$485.25	$485.20