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	$75.41	4.693%	$78.949	$78.95	$78.95	$78.90
Purchase #2	$52.52	12.239%	$58.9479	$58.95	$58.95	$58.90
Purchase #3	$71.56	13.342%	$81.1075	$81.11	$81.10	$81.10
Purchase #4	$50.82	4.210%	$52.9595	$52.96	$52.95	$53.00
Purchase #5	$169.39	11.282%	$188.5006	$188.50	$188.50	$188.50
Purchase #6	$54.43	9.248%	$59.4637	$59.46	$59.45	$59.50
Purchase #7	$132.58	10.498%	$146.4982	$146.50	$146.50	$146.50
7 purchase totals =	$606.71		$666.4264	$666.43	$666.40	$666.40