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	$169.64	8.560%	$184.1612	$184.16	$184.15	$184.20
Purchase #2	$170.72	13.725%	$194.1513	$194.15	$194.15	$194.20
Purchase #3	$51.76	4.586%	$54.1337	$54.13	$54.15	$54.10
Purchase #4	$99.27	3.348%	$102.5936	$102.59	$102.60	$102.60
Purchase #5	$68.54	3.781%	$71.1315	$71.13	$71.15	$71.10
Purchase #6	$90.66	5.375%	$95.533	$95.53	$95.55	$95.50
Purchase #7	$193.52	9.455%	$211.8173	$211.82	$211.80	$211.80
7 purchase totals =	$844.11		$913.5216	$913.51	$913.55	$913.50