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	$93.95	5.349%	$98.9754	$98.98	$99.00	$99.00
Purchase #2	$81.28	3.225%	$83.9013	$83.90	$83.90	$83.90
Purchase #3	$89.94	5.251%	$94.6627	$94.66	$94.65	$94.70
Purchase #4	$245.82	11.392%	$273.8238	$273.82	$273.80	$273.80
Purchase #5	$154.51	8.368%	$167.4394	$167.44	$167.45	$167.40
Purchase #6	$162.82	7.451%	$174.9517	$174.95	$174.95	$175.00
Purchase #7	$162.42	3.230%	$167.6662	$167.67	$167.65	$167.70
7 purchase totals =	$990.74		$1,061.4205	$1,061.42	$1,061.40	$1,061.50