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	$153.63	9.430%	$168.1173	$168.12	$168.10	$168.10
Purchase #2	$113.45	4.462%	$118.5121	$118.51	$118.50	$118.50
Purchase #3	$12.97	9.503%	$14.2025	$14.20	$14.20	$14.20
Purchase #4	$133.63	12.481%	$150.3084	$150.31	$150.30	$150.30
Purchase #5	$144.43	5.199%	$151.9389	$151.94	$151.95	$151.90
Purchase #6	$94.78	6.655%	$101.0876	$101.09	$101.10	$101.10
Purchase #7	$96.38	4.655%	$100.8665	$100.87	$100.85	$100.90
7 purchase totals =	$749.27		$805.0333	$805.04	$805.00	$805.00