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	$41.61	12.455%	$46.7925	$46.79	$46.80	$46.80
Purchase #2	$72.55	7.441%	$77.9484	$77.95	$77.95	$77.90
Purchase #3	$235.98	3.684%	$244.6735	$244.67	$244.65	$244.70
Purchase #4	$114.40	3.600%	$118.5184	$118.52	$118.50	$118.50
Purchase #5	$117.41	8.241%	$127.0858	$127.09	$127.10	$127.10
Purchase #6	$32.90	12.514%	$37.0171	$37.02	$37.00	$37.00
Purchase #7	$54.79	8.701%	$59.5573	$59.56	$59.55	$59.60
7 purchase totals =	$669.64		$711.5930	$711.60	$711.55	$711.60