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	$75.64	9.542%	$82.8576	$82.86	$82.85	$82.90
Purchase #2	$20.64	10.810%	$22.8712	$22.87	$22.85	$22.90
Purchase #3	$90.66	11.818%	$101.3742	$101.37	$101.35	$101.40
Purchase #4	$202.75	10.255%	$223.542	$223.54	$223.55	$223.50
Purchase #5	$36.79	12.236%	$41.2916	$41.29	$41.30	$41.30
Purchase #6	$172.47	6.217%	$183.1925	$183.19	$183.20	$183.20
Purchase #7	$159.83	13.385%	$181.2232	$181.22	$181.20	$181.20
7 purchase totals =	$758.78		$836.3523	$836.34	$836.30	$836.40