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	$67.48	7.549%	$72.5741	$72.57	$72.55	$72.60
Purchase #2	$202.97	5.366%	$213.8614	$213.86	$213.85	$213.90
Purchase #3	$144.73	5.792%	$153.1128	$153.11	$153.10	$153.10
Purchase #4	$117.80	13.248%	$133.4061	$133.41	$133.40	$133.40
Purchase #5	$132.44	4.120%	$137.8965	$137.90	$137.90	$137.90
Purchase #6	$232.57	7.862%	$250.8547	$250.85	$250.85	$250.90
Purchase #7	$80.85	11.104%	$89.8276	$89.83	$89.85	$89.80
7 purchase totals =	$978.84		$1,051.5332	$1,051.53	$1,051.50	$1,051.60