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	$189.69	11.115%	$210.774	$210.77	$210.75	$210.80
Purchase #2	$94.75	11.140%	$105.3052	$105.31	$105.30	$105.30
Purchase #3	$159.33	4.724%	$166.8567	$166.86	$166.85	$166.90
Purchase #4	$189.33	3.773%	$196.4734	$196.47	$196.45	$196.50
Purchase #5	$164.32	11.682%	$183.5159	$183.52	$183.50	$183.50
Purchase #6	$116.52	5.336%	$122.7375	$122.74	$122.75	$122.70
Purchase #7	$86.78	8.618%	$94.2587	$94.26	$94.25	$94.30
7 purchase totals =	$1,000.72		$1,079.9214	$1,079.93	$1,079.85	$1,080.00