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	$43.30	7.342%	$46.4791	$46.48	$46.50	$46.50
Purchase #2	$196.37	4.404%	$205.0181	$205.02	$205.00	$205.00
Purchase #3	$131.79	6.732%	$140.6621	$140.66	$140.65	$140.70
Purchase #4	$65.31	4.729%	$68.3985	$68.40	$68.40	$68.40
Purchase #5	$196.30	13.233%	$222.2764	$222.28	$222.30	$222.30
Purchase #6	$207.50	12.595%	$233.6346	$233.63	$233.65	$233.60
Purchase #7	$243.50	5.458%	$256.7902	$256.79	$256.80	$256.80
7 purchase totals =	$1,084.07		$1,173.2590	$1,173.26	$1,173.30	$1,173.30