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	$173.90	7.201%	$186.4225	$186.42	$186.40	$186.40
Purchase #2	$128.87	6.208%	$136.8702	$136.87	$136.85	$136.90
Purchase #3	$57.67	13.320%	$65.3516	$65.35	$65.35	$65.40
Purchase #4	$250.95	8.665%	$272.6948	$272.69	$272.70	$272.70
Purchase #5	$204.58	8.736%	$222.4521	$222.45	$222.45	$222.50
Purchase #6	$53.68	4.383%	$56.0328	$56.03	$56.05	$56.00
Purchase #7	$92.59	11.576%	$103.3082	$103.31	$103.30	$103.30
7 purchase totals =	$962.24		$1,043.1322	$1,043.12	$1,043.10	$1,043.20