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	$75.90	10.107%	$83.5712	$83.57	$83.55	$83.60
Purchase #2	$23.76	3.120%	$24.5013	$24.50	$24.50	$24.50
Purchase #3	$143.74	3.726%	$149.0958	$149.10	$149.10	$149.10
Purchase #4	$148.82	12.431%	$167.3198	$167.32	$167.30	$167.30
Purchase #5	$142.97	12.530%	$160.8841	$160.88	$160.90	$160.90
Purchase #6	$198.42	10.232%	$218.7223	$218.72	$218.70	$218.70
Purchase #7	$172.54	13.820%	$196.385	$196.39	$196.40	$196.40
7 purchase totals =	$906.15		$1,000.4795	$1,000.48	$1,000.45	$1,000.50