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	$141.43	4.482%	$147.7689	$147.77	$147.75	$147.80
Purchase #2	$28.75	10.495%	$31.7673	$31.77	$31.75	$31.80
Purchase #3	$101.59	7.199%	$108.9035	$108.90	$108.90	$108.90
Purchase #4	$189.98	3.328%	$196.3025	$196.30	$196.30	$196.30
Purchase #5	$150.53	9.741%	$165.1931	$165.19	$165.20	$165.20
Purchase #6	$206.78	3.769%	$214.5735	$214.57	$214.55	$214.60
Purchase #7	$103.85	6.736%	$110.8453	$110.85	$110.85	$110.80
7 purchase totals =	$922.91		$975.3541	$975.35	$975.30	$975.40