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	$51.78	3.815%	$53.7554	$53.76	$53.75	$53.80
Purchase #2	$38.98	9.398%	$42.6433	$42.64	$42.65	$42.60
Purchase #3	$150.98	7.602%	$162.4575	$162.46	$162.45	$162.50
Purchase #4	$163.31	11.179%	$181.5664	$181.57	$181.55	$181.60
Purchase #5	$7.39	4.193%	$7.6999	$7.70	$7.70	$7.70
Purchase #6	$214.35	4.447%	$223.8821	$223.88	$223.90	$223.90
Purchase #7	$229.89	11.265%	$255.7871	$255.79	$255.80	$255.80
7 purchase totals =	$856.68		$927.7917	$927.80	$927.80	$927.90