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	$63.68	4.827%	$66.7538	$66.75	$66.75	$66.80
Purchase #2	$82.76	3.433%	$85.6012	$85.60	$85.60	$85.60
Purchase #3	$98.55	4.135%	$102.625	$102.63	$102.65	$102.60
Purchase #4	$237.75	4.488%	$248.4202	$248.42	$248.40	$248.40
Purchase #5	$61.70	12.241%	$69.2527	$69.25	$69.25	$69.30
Purchase #6	$241.51	9.501%	$264.4559	$264.46	$264.45	$264.50
Purchase #7	$83.89	13.624%	$95.3192	$95.32	$95.30	$95.30
7 purchase totals =	$869.84		$932.4280	$932.43	$932.40	$932.50