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	$207.33	5.781%	$219.3157	$219.32	$219.30	$219.30
Purchase #2	$55.51	9.723%	$60.9072	$60.91	$60.90	$60.90
Purchase #3	$238.36	11.846%	$266.5961	$266.60	$266.60	$266.60
Purchase #4	$153.91	6.870%	$164.4836	$164.48	$164.50	$164.50
Purchase #5	$47.53	12.742%	$53.5863	$53.59	$53.60	$53.60
Purchase #6	$12.33	12.343%	$13.8519	$13.85	$13.85	$13.90
Purchase #7	$203.57	12.530%	$229.0773	$229.08	$229.10	$229.10
7 purchase totals =	$918.54		$1,007.8181	$1,007.83	$1,007.85	$1,007.90