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	$190.60	5.121%	$200.3606	$200.36	$200.35	$200.40
Purchase #2	$133.54	13.212%	$151.1833	$151.18	$151.20	$151.20
Purchase #3	$71.50	10.219%	$78.8066	$78.81	$78.80	$78.80
Purchase #4	$5.74	11.265%	$6.3866	$6.39	$6.40	$6.40
Purchase #5	$134.76	13.372%	$152.7801	$152.78	$152.80	$152.80
Purchase #6	$83.51	3.298%	$86.2642	$86.26	$86.25	$86.30
Purchase #7	$119.64	12.781%	$134.9312	$134.93	$134.95	$134.90
7 purchase totals =	$739.29		$810.7126	$810.71	$810.75	$810.80