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	$100.62	7.828%	$108.4965	$108.50	$108.50	$108.50
Purchase #2	$235.27	10.130%	$259.1029	$259.10	$259.10	$259.10
Purchase #3	$121.63	8.651%	$132.1522	$132.15	$132.15	$132.20
Purchase #4	$50.60	9.496%	$55.405	$55.41	$55.40	$55.40
Purchase #5	$213.94	13.786%	$243.4338	$243.43	$243.45	$243.40
Purchase #6	$207.66	12.556%	$233.7338	$233.73	$233.75	$233.70
Purchase #7	$117.84	5.132%	$123.8875	$123.89	$123.90	$123.90
7 purchase totals =	$1,047.56		$1,156.2117	$1,156.21	$1,156.25	$1,156.20