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	$79.50	11.111%	$88.3332	$88.33	$88.35	$88.30
Purchase #2	$157.95	7.445%	$169.7094	$169.71	$169.70	$169.70
Purchase #3	$34.39	7.629%	$37.0136	$37.01	$37.00	$37.00
Purchase #4	$222.47	12.214%	$249.6425	$249.64	$249.65	$249.60
Purchase #5	$229.69	3.133%	$236.8862	$236.89	$236.90	$236.90
Purchase #6	$73.77	6.539%	$78.5938	$78.59	$78.60	$78.60
Purchase #7	$164.33	13.393%	$186.3387	$186.34	$186.35	$186.30
7 purchase totals =	$962.10		$1,046.5174	$1,046.51	$1,046.55	$1,046.40