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	$127.79	3.588%	$132.3751	$132.38	$132.40	$132.40
Purchase #2	$238.81	6.311%	$253.8813	$253.88	$253.90	$253.90
Purchase #3	$180.71	8.168%	$195.4704	$195.47	$195.45	$195.50
Purchase #4	$62.44	4.627%	$65.3291	$65.33	$65.35	$65.30
Purchase #5	$60.64	8.449%	$65.7635	$65.76	$65.75	$65.80
Purchase #6	$123.92	5.762%	$131.0603	$131.06	$131.05	$131.10
Purchase #7	$85.61	8.539%	$92.9202	$92.92	$92.90	$92.90
7 purchase totals =	$879.92		$936.7999	$936.80	$936.80	$936.90