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	$101.54	10.198%	$111.895	$111.90	$111.90	$111.90
Purchase #2	$168.97	9.810%	$185.546	$185.55	$185.55	$185.50
Purchase #3	$95.98	4.465%	$100.2655	$100.27	$100.25	$100.30
Purchase #4	$62.65	12.673%	$70.5896	$70.59	$70.60	$70.60
Purchase #5	$22.59	13.382%	$25.613	$25.61	$25.60	$25.60
Purchase #6	$67.41	4.496%	$70.4408	$70.44	$70.45	$70.40
Purchase #7	$180.31	10.275%	$198.8369	$198.84	$198.85	$198.80
7 purchase totals =	$699.45		$763.1868	$763.20	$763.20	$763.10