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	$172.25	7.158%	$184.5797	$184.58	$184.60	$184.60
Purchase #2	$208.87	6.534%	$222.5176	$222.52	$222.50	$222.50
Purchase #3	$194.49	8.471%	$210.9652	$210.97	$210.95	$211.00
Purchase #4	$223.66	7.241%	$239.8552	$239.86	$239.85	$239.90
Purchase #5	$122.87	7.281%	$131.8162	$131.82	$131.80	$131.80
Purchase #6	$31.29	8.541%	$33.9625	$33.96	$33.95	$34.00
Purchase #7	$52.95	7.410%	$56.8736	$56.87	$56.85	$56.90
7 purchase totals =	$1,006.38		$1,080.5700	$1,080.58	$1,080.50	$1,080.70