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	$177.70	12.215%	$199.4061	$199.41	$199.40	$199.40
Purchase #2	$226.56	4.752%	$237.3261	$237.33	$237.35	$237.30
Purchase #3	$59.45	13.725%	$67.6095	$67.61	$67.60	$67.60
Purchase #4	$80.33	13.637%	$91.2846	$91.28	$91.30	$91.30
Purchase #5	$128.44	12.287%	$144.2214	$144.22	$144.20	$144.20
Purchase #6	$211.32	7.645%	$227.4754	$227.48	$227.50	$227.50
Purchase #7	$178.77	10.842%	$198.1522	$198.15	$198.15	$198.20
7 purchase totals =	$1,062.57		$1,165.4753	$1,165.48	$1,165.50	$1,165.50