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	$236.93	3.662%	$245.6064	$245.61	$245.60	$245.60
Purchase #2	$18.78	11.447%	$20.9297	$20.93	$20.95	$20.90
Purchase #3	$200.55	13.322%	$227.2673	$227.27	$227.25	$227.30
Purchase #4	$76.87	11.440%	$85.6639	$85.66	$85.65	$85.70
Purchase #5	$153.44	3.115%	$158.2197	$158.22	$158.20	$158.20
Purchase #6	$140.39	8.178%	$151.8711	$151.87	$151.85	$151.90
Purchase #7	$157.94	6.135%	$167.6296	$167.63	$167.65	$167.60
7 purchase totals =	$984.90		$1,057.1877	$1,057.19	$1,057.15	$1,057.20