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	$92.26	12.773%	$104.0444	$104.04	$104.05	$104.00
Purchase #2	$60.94	7.752%	$65.6641	$65.66	$65.65	$65.70
Purchase #3	$30.53	9.425%	$33.4075	$33.41	$33.40	$33.40
Purchase #4	$56.86	4.818%	$59.5995	$59.60	$59.60	$59.60
Purchase #5	$147.50	3.457%	$152.5991	$152.60	$152.60	$152.60
Purchase #6	$29.94	6.370%	$31.8472	$31.85	$31.85	$31.80
Purchase #7	$40.39	7.622%	$43.4685	$43.47	$43.45	$43.50
7 purchase totals =	$458.42		$490.6303	$490.63	$490.60	$490.60