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	$124.49	5.751%	$131.6494	$131.65	$131.65	$131.60
Purchase #2	$131.89	9.548%	$144.4829	$144.48	$144.50	$144.50
Purchase #3	$161.71	8.420%	$175.326	$175.33	$175.35	$175.30
Purchase #4	$74.38	7.631%	$80.0559	$80.06	$80.05	$80.10
Purchase #5	$218.46	3.164%	$225.3721	$225.37	$225.35	$225.40
Purchase #6	$214.27	13.115%	$242.3715	$242.37	$242.35	$242.40
Purchase #7	$18.67	5.179%	$19.6369	$19.64	$19.65	$19.60
7 purchase totals =	$943.87		$1,018.8947	$1,018.90	$1,018.90	$1,018.90