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	$232.38	10.228%	$256.1478	$256.15	$256.15	$256.10
Purchase #2	$214.58	11.639%	$239.555	$239.56	$239.55	$239.60
Purchase #3	$78.41	10.395%	$86.5607	$86.56	$86.55	$86.60
Purchase #4	$82.46	13.624%	$93.6944	$93.69	$93.70	$93.70
Purchase #5	$37.40	13.722%	$42.532	$42.53	$42.55	$42.50
Purchase #6	$167.28	11.840%	$187.086	$187.09	$187.10	$187.10
Purchase #7	$216.76	11.368%	$241.4013	$241.40	$241.40	$241.40
7 purchase totals =	$1,029.27		$1,146.9772	$1,146.98	$1,147.00	$1,147.00