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	$175.80	5.323%	$185.1578	$185.16	$185.15	$185.20
Purchase #2	$130.83	8.729%	$142.2502	$142.25	$142.25	$142.30
Purchase #3	$83.55	13.543%	$94.8652	$94.87	$94.85	$94.90
Purchase #4	$18.47	8.709%	$20.0786	$20.08	$20.10	$20.10
Purchase #5	$89.94	5.193%	$94.6106	$94.61	$94.60	$94.60
Purchase #6	$180.77	5.696%	$191.0667	$191.07	$191.05	$191.10
Purchase #7	$36.71	13.167%	$41.5436	$41.54	$41.55	$41.50
7 purchase totals =	$716.07		$769.5727	$769.58	$769.55	$769.70