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	$238.43	12.423%	$268.0502	$268.05	$268.05	$268.10
Purchase #2	$43.46	3.296%	$44.8924	$44.89	$44.90	$44.90
Purchase #3	$9.93	4.528%	$10.3796	$10.38	$10.40	$10.40
Purchase #4	$91.33	7.726%	$98.3862	$98.39	$98.40	$98.40
Purchase #5	$144.76	4.310%	$150.9992	$151.00	$151.00	$151.00
Purchase #6	$232.39	13.410%	$263.5535	$263.55	$263.55	$263.60
Purchase #7	$28.31	9.853%	$31.0994	$31.10	$31.10	$31.10
7 purchase totals =	$788.61		$867.3605	$867.36	$867.40	$867.50