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	$160.72	13.695%	$182.7306	$182.73	$182.75	$182.70
Purchase #2	$85.97	4.332%	$89.6942	$89.69	$89.70	$89.70
Purchase #3	$156.65	8.259%	$169.5877	$169.59	$169.60	$169.60
Purchase #4	$122.90	4.827%	$128.8324	$128.83	$128.85	$128.80
Purchase #5	$108.28	5.331%	$114.0524	$114.05	$114.05	$114.10
Purchase #6	$94.61	5.650%	$99.9555	$99.96	$99.95	$100.00
Purchase #7	$6.56	12.389%	$7.3727	$7.37	$7.35	$7.40
7 purchase totals =	$735.69		$792.2255	$792.22	$792.25	$792.30