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	$49.82	5.665%	$52.6423	$52.64	$52.65	$52.60
Purchase #2	$169.40	8.276%	$183.4195	$183.42	$183.40	$183.40
Purchase #3	$40.33	5.461%	$42.5324	$42.53	$42.55	$42.50
Purchase #4	$178.47	6.393%	$189.8796	$189.88	$189.90	$189.90
Purchase #5	$97.26	6.680%	$103.757	$103.76	$103.75	$103.80
Purchase #6	$114.45	8.705%	$124.4129	$124.41	$124.40	$124.40
Purchase #7	$165.55	12.238%	$185.81	$185.81	$185.80	$185.80
7 purchase totals =	$815.28		$882.4537	$882.45	$882.45	$882.40