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	$95.65	12.736%	$107.832	$107.83	$107.85	$107.80
Purchase #2	$18.49	9.366%	$20.2218	$20.22	$20.20	$20.20
Purchase #3	$195.85	6.221%	$208.0338	$208.03	$208.05	$208.00
Purchase #4	$47.86	10.780%	$53.0193	$53.02	$53.00	$53.00
Purchase #5	$249.56	11.550%	$278.3842	$278.38	$278.40	$278.40
Purchase #6	$176.52	7.766%	$190.2285	$190.23	$190.25	$190.20
Purchase #7	$41.79	3.334%	$43.1833	$43.18	$43.20	$43.20
7 purchase totals =	$825.72		$900.9029	$900.89	$900.95	$900.80