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	$58.72	11.414%	$65.4223	$65.42	$65.40	$65.40
Purchase #2	$172.98	13.842%	$196.9239	$196.92	$196.90	$196.90
Purchase #3	$75.72	8.769%	$82.3599	$82.36	$82.35	$82.40
Purchase #4	$62.73	10.304%	$69.1937	$69.19	$69.20	$69.20
Purchase #5	$165.72	10.769%	$183.5664	$183.57	$183.55	$183.60
Purchase #6	$160.74	12.281%	$180.4805	$180.48	$180.50	$180.50
Purchase #7	$145.97	5.261%	$153.6495	$153.65	$153.65	$153.60
7 purchase totals =	$842.58		$931.5962	$931.59	$931.55	$931.60