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	$67.61	8.446%	$73.3203	$73.32	$73.30	$73.30
Purchase #2	$168.31	10.849%	$186.57	$186.57	$186.55	$186.60
Purchase #3	$52.35	4.566%	$54.7403	$54.74	$54.75	$54.70
Purchase #4	$241.98	11.772%	$270.4659	$270.47	$270.45	$270.50
Purchase #5	$193.93	12.667%	$218.4951	$218.50	$218.50	$218.50
Purchase #6	$159.63	7.630%	$171.8098	$171.81	$171.80	$171.80
Purchase #7	$69.66	3.477%	$72.0821	$72.08	$72.10	$72.10
7 purchase totals =	$953.47		$1,047.4835	$1,047.49	$1,047.45	$1,047.50