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	$147.79	12.818%	$166.7337	$166.73	$166.75	$166.70
Purchase #2	$99.66	12.748%	$112.3647	$112.36	$112.35	$112.40
Purchase #3	$122.32	7.412%	$131.3864	$131.39	$131.40	$131.40
Purchase #4	$134.75	9.111%	$147.0271	$147.03	$147.05	$147.00
Purchase #5	$69.34	10.515%	$76.6311	$76.63	$76.65	$76.60
Purchase #6	$222.48	7.142%	$238.3695	$238.37	$238.35	$238.40
Purchase #7	$196.32	9.136%	$214.2558	$214.26	$214.25	$214.30
7 purchase totals =	$992.66		$1,086.7683	$1,086.77	$1,086.80	$1,086.80