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	$180.41	8.413%	$195.5879	$195.59	$195.60	$195.60
Purchase #2	$63.27	3.183%	$65.2839	$65.28	$65.30	$65.30
Purchase #3	$95.81	5.112%	$100.7078	$100.71	$100.70	$100.70
Purchase #4	$84.48	13.388%	$95.7902	$95.79	$95.80	$95.80
Purchase #5	$168.63	12.583%	$189.8487	$189.85	$189.85	$189.80
Purchase #6	$241.28	5.393%	$254.2922	$254.29	$254.30	$254.30
Purchase #7	$185.37	7.458%	$199.1949	$199.19	$199.20	$199.20
7 purchase totals =	$1,019.25		$1,100.7056	$1,100.70	$1,100.75	$1,100.70