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	$10.88	4.623%	$11.383	$11.38	$11.40	$11.40
Purchase #2	$187.43	10.175%	$206.501	$206.50	$206.50	$206.50
Purchase #3	$49.98	8.691%	$54.3238	$54.32	$54.30	$54.30
Purchase #4	$139.88	5.643%	$147.7734	$147.77	$147.75	$147.80
Purchase #5	$152.78	6.609%	$162.8772	$162.88	$162.90	$162.90
Purchase #6	$103.79	7.534%	$111.6095	$111.61	$111.60	$111.60
Purchase #7	$175.99	7.520%	$189.2244	$189.22	$189.20	$189.20
7 purchase totals =	$820.73		$883.6923	$883.68	$883.65	$883.70