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	$209.86	8.590%	$227.887	$227.89	$227.90	$227.90
Purchase #2	$149.30	8.806%	$162.4474	$162.45	$162.45	$162.40
Purchase #3	$150.87	10.604%	$166.8683	$166.87	$166.85	$166.90
Purchase #4	$166.87	8.165%	$180.4949	$180.49	$180.50	$180.50
Purchase #5	$136.36	6.205%	$144.8211	$144.82	$144.80	$144.80
Purchase #6	$61.44	9.640%	$67.3628	$67.36	$67.35	$67.40
Purchase #7	$208.68	10.155%	$229.8715	$229.87	$229.85	$229.90
7 purchase totals =	$1,083.38		$1,179.7530	$1,179.75	$1,179.70	$1,179.80