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	$50.77	6.709%	$54.1762	$54.18	$54.20	$54.20
Purchase #2	$123.68	3.835%	$128.4231	$128.42	$128.40	$128.40
Purchase #3	$205.44	6.134%	$218.0417	$218.04	$218.05	$218.00
Purchase #4	$95.34	5.558%	$100.639	$100.64	$100.65	$100.60
Purchase #5	$82.70	7.814%	$89.1622	$89.16	$89.15	$89.20
Purchase #6	$100.25	6.376%	$106.6419	$106.64	$106.65	$106.60
Purchase #7	$226.28	4.477%	$236.4106	$236.41	$236.40	$236.40
7 purchase totals =	$884.46		$933.4947	$933.49	$933.50	$933.40