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	$99.82	11.275%	$111.0747	$111.07	$111.05	$111.10
Purchase #2	$16.69	10.754%	$18.4848	$18.48	$18.50	$18.50
Purchase #3	$240.53	3.810%	$249.6942	$249.69	$249.70	$249.70
Purchase #4	$107.53	7.736%	$115.8485	$115.85	$115.85	$115.80
Purchase #5	$72.97	13.542%	$82.8516	$82.85	$82.85	$82.90
Purchase #6	$109.51	3.414%	$113.2487	$113.25	$113.25	$113.20
Purchase #7	$203.36	13.862%	$231.5498	$231.55	$231.55	$231.50
7 purchase totals =	$850.41		$922.7523	$922.74	$922.75	$922.70