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	$163.36	4.742%	$171.1065	$171.11	$171.10	$171.10
Purchase #2	$203.64	9.247%	$222.4706	$222.47	$222.45	$222.50
Purchase #3	$130.66	9.648%	$143.2661	$143.27	$143.25	$143.30
Purchase #4	$196.84	7.333%	$211.2743	$211.27	$211.25	$211.30
Purchase #5	$60.62	10.404%	$66.9269	$66.93	$66.95	$66.90
Purchase #6	$129.90	11.496%	$144.8333	$144.83	$144.85	$144.80
Purchase #7	$120.67	12.791%	$136.1049	$136.10	$136.10	$136.10
7 purchase totals =	$1,005.69		$1,095.9826	$1,095.98	$1,095.95	$1,096.00