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	$187.50	4.843%	$196.5806	$196.58	$196.60	$196.60
Purchase #2	$19.79	3.787%	$20.5394	$20.54	$20.55	$20.50
Purchase #3	$122.57	7.773%	$132.0974	$132.10	$132.10	$132.10
Purchase #4	$230.46	10.373%	$254.3656	$254.37	$254.35	$254.40
Purchase #5	$250.50	4.212%	$261.0511	$261.05	$261.05	$261.10
Purchase #6	$85.48	3.173%	$88.1923	$88.19	$88.20	$88.20
Purchase #7	$117.60	12.153%	$131.8919	$131.89	$131.90	$131.90
7 purchase totals =	$1,013.90		$1,084.7183	$1,084.72	$1,084.75	$1,084.80