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	$198.87	12.563%	$223.854	$223.85	$223.85	$223.90
Purchase #2	$38.90	11.845%	$43.5077	$43.51	$43.50	$43.50
Purchase #3	$58.72	8.288%	$63.5867	$63.59	$63.60	$63.60
Purchase #4	$234.37	6.823%	$250.3611	$250.36	$250.35	$250.40
Purchase #5	$151.53	9.713%	$166.2481	$166.25	$166.25	$166.20
Purchase #6	$150.29	8.218%	$162.6408	$162.64	$162.65	$162.60
Purchase #7	$125.70	5.364%	$132.4425	$132.44	$132.45	$132.40
7 purchase totals =	$958.38		$1,042.6409	$1,042.64	$1,042.65	$1,042.60