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	$175.63	5.424%	$185.1562	$185.16	$185.15	$185.20
Purchase #2	$94.92	12.779%	$107.0498	$107.05	$107.05	$107.00
Purchase #3	$172.99	13.424%	$196.2122	$196.21	$196.20	$196.20
Purchase #4	$61.48	6.343%	$65.3797	$65.38	$65.40	$65.40
Purchase #5	$142.91	9.644%	$156.6922	$156.69	$156.70	$156.70
Purchase #6	$95.91	8.290%	$103.8609	$103.86	$103.85	$103.90
Purchase #7	$31.59	9.334%	$34.5386	$34.54	$34.55	$34.50
7 purchase totals =	$775.43		$848.8896	$848.89	$848.90	$848.90