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	$86.31	11.812%	$96.5049	$96.50	$96.50	$96.50
Purchase #2	$162.61	11.656%	$181.5638	$181.56	$181.55	$181.60
Purchase #3	$95.70	7.256%	$102.644	$102.64	$102.65	$102.60
Purchase #4	$247.42	7.638%	$266.3179	$266.32	$266.30	$266.30
Purchase #5	$41.55	3.152%	$42.8597	$42.86	$42.85	$42.90
Purchase #6	$105.89	12.146%	$118.7514	$118.75	$118.75	$118.80
Purchase #7	$152.35	6.765%	$162.6565	$162.66	$162.65	$162.70
7 purchase totals =	$891.83		$971.2982	$971.29	$971.25	$971.40