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	$167.77	9.780%	$184.1779	$184.18	$184.20	$184.20
Purchase #2	$145.89	13.331%	$165.3386	$165.34	$165.35	$165.30
Purchase #3	$27.38	4.655%	$28.6545	$28.65	$28.65	$28.70
Purchase #4	$194.99	13.509%	$221.3312	$221.33	$221.35	$221.30
Purchase #5	$80.98	12.208%	$90.866	$90.87	$90.85	$90.90
Purchase #6	$189.34	12.377%	$212.7746	$212.77	$212.75	$212.80
Purchase #7	$185.37	9.262%	$202.539	$202.54	$202.55	$202.50
7 purchase totals =	$991.72		$1,105.6818	$1,105.68	$1,105.70	$1,105.70