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	$53.83	13.630%	$61.167	$61.17	$61.15	$61.20
Purchase #2	$127.52	11.227%	$141.8367	$141.84	$141.85	$141.80
Purchase #3	$38.50	6.516%	$41.0087	$41.01	$41.00	$41.00
Purchase #4	$138.92	4.473%	$145.1339	$145.13	$145.15	$145.10
Purchase #5	$182.53	3.747%	$189.3694	$189.37	$189.35	$189.40
Purchase #6	$158.85	4.701%	$166.3175	$166.32	$166.30	$166.30
Purchase #7	$249.79	9.303%	$273.028	$273.03	$273.05	$273.00
7 purchase totals =	$949.94		$1,017.8612	$1,017.87	$1,017.85	$1,017.80