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	$157.50	4.476%	$164.5497	$164.55	$164.55	$164.50
Purchase #2	$236.75	6.682%	$252.5696	$252.57	$252.55	$252.60
Purchase #3	$213.51	11.515%	$238.0957	$238.10	$238.10	$238.10
Purchase #4	$67.67	5.487%	$71.3831	$71.38	$71.40	$71.40
Purchase #5	$79.36	3.744%	$82.3312	$82.33	$82.35	$82.30
Purchase #6	$94.91	5.457%	$100.0892	$100.09	$100.10	$100.10
Purchase #7	$126.92	4.377%	$132.4753	$132.48	$132.50	$132.50
7 purchase totals =	$976.62		$1,041.4938	$1,041.50	$1,041.55	$1,041.50