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	$166.43	10.478%	$183.8685	$183.87	$183.85	$183.90
Purchase #2	$176.30	6.323%	$187.4474	$187.45	$187.45	$187.40
Purchase #3	$40.49	11.113%	$44.9897	$44.99	$45.00	$45.00
Purchase #4	$129.92	7.115%	$139.1638	$139.16	$139.15	$139.20
Purchase #5	$82.53	12.716%	$93.0245	$93.02	$93.00	$93.00
Purchase #6	$172.82	13.423%	$196.0176	$196.02	$196.00	$196.00
Purchase #7	$88.85	13.173%	$100.5542	$100.55	$100.55	$100.60
7 purchase totals =	$857.34		$945.0657	$945.06	$945.00	$945.10