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	$165.37	11.375%	$184.1808	$184.18	$184.20	$184.20
Purchase #2	$213.56	8.405%	$231.5097	$231.51	$231.50	$231.50
Purchase #3	$70.55	11.715%	$78.8149	$78.81	$78.80	$78.80
Purchase #4	$246.57	9.703%	$270.4947	$270.49	$270.50	$270.50
Purchase #5	$200.36	10.475%	$221.3477	$221.35	$221.35	$221.30
Purchase #6	$74.52	5.226%	$78.4144	$78.41	$78.40	$78.40
Purchase #7	$188.31	4.566%	$196.9082	$196.91	$196.90	$196.90
7 purchase totals =	$1,159.24		$1,261.6704	$1,261.66	$1,261.65	$1,261.60