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	$229.92	3.591%	$238.1764	$238.18	$238.20	$238.20
Purchase #2	$48.79	13.772%	$55.5094	$55.51	$55.50	$55.50
Purchase #3	$79.79	4.806%	$83.6247	$83.62	$83.60	$83.60
Purchase #4	$209.93	4.434%	$219.2383	$219.24	$219.25	$219.20
Purchase #5	$72.50	8.754%	$78.8467	$78.85	$78.85	$78.80
Purchase #6	$171.76	8.460%	$186.2909	$186.29	$186.30	$186.30
Purchase #7	$75.79	5.250%	$79.769	$79.77	$79.75	$79.80
7 purchase totals =	$888.48		$941.4554	$941.46	$941.45	$941.40