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	$43.60	3.605%	$45.1718	$45.17	$45.15	$45.20
Purchase #2	$160.79	11.627%	$179.4851	$179.49	$179.50	$179.50
Purchase #3	$145.25	3.797%	$150.7651	$150.77	$150.75	$150.80
Purchase #4	$162.32	4.554%	$169.7121	$169.71	$169.70	$169.70
Purchase #5	$148.30	12.773%	$167.2424	$167.24	$167.25	$167.20
Purchase #6	$236.55	12.351%	$265.7663	$265.77	$265.75	$265.80
Purchase #7	$143.49	9.207%	$156.7011	$156.70	$156.70	$156.70
7 purchase totals =	$1,040.30		$1,134.8439	$1,134.85	$1,134.80	$1,134.90