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	$52.26	13.636%	$59.3862	$59.39	$59.40	$59.40
Purchase #2	$147.99	12.700%	$166.7847	$166.78	$166.80	$166.80
Purchase #3	$238.89	5.481%	$251.9836	$251.98	$252.00	$252.00
Purchase #4	$241.26	12.587%	$271.6274	$271.63	$271.65	$271.60
Purchase #5	$71.80	11.845%	$80.3047	$80.30	$80.30	$80.30
Purchase #6	$200.38	4.471%	$209.339	$209.34	$209.35	$209.30
Purchase #7	$34.89	7.618%	$37.5479	$37.55	$37.55	$37.50
7 purchase totals =	$987.47		$1,076.9735	$1,076.97	$1,077.05	$1,076.90