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	$126.69	13.321%	$143.5664	$143.57	$143.55	$143.60
Purchase #2	$162.98	10.128%	$179.4866	$179.49	$179.50	$179.50
Purchase #3	$220.25	12.809%	$248.4618	$248.46	$248.45	$248.50
Purchase #4	$96.78	8.797%	$105.2937	$105.29	$105.30	$105.30
Purchase #5	$180.29	13.117%	$203.9386	$203.94	$203.95	$203.90
Purchase #6	$163.99	6.874%	$175.2627	$175.26	$175.25	$175.30
Purchase #7	$40.32	7.407%	$43.3065	$43.31	$43.30	$43.30
7 purchase totals =	$991.30		$1,099.3163	$1,099.32	$1,099.30	$1,099.40