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	$233.55	5.573%	$246.5657	$246.57	$246.55	$246.60
Purchase #2	$60.40	7.710%	$65.0568	$65.06	$65.05	$65.10
Purchase #3	$101.52	4.280%	$105.8651	$105.87	$105.85	$105.90
Purchase #4	$182.72	7.540%	$196.4971	$196.50	$196.50	$196.50
Purchase #5	$234.63	11.569%	$261.7743	$261.77	$261.75	$261.80
Purchase #6	$126.93	10.615%	$140.4036	$140.40	$140.40	$140.40
Purchase #7	$17.87	10.401%	$19.7287	$19.73	$19.75	$19.70
7 purchase totals =	$957.62		$1,035.8913	$1,035.90	$1,035.85	$1,036.00