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	$78.31	6.422%	$83.3391	$83.34	$83.35	$83.30
Purchase #2	$175.28	11.168%	$194.8553	$194.86	$194.85	$194.90
Purchase #3	$40.85	6.818%	$43.6352	$43.64	$43.65	$43.60
Purchase #4	$45.43	6.357%	$48.318	$48.32	$48.30	$48.30
Purchase #5	$204.94	8.683%	$222.7349	$222.73	$222.75	$222.70
Purchase #6	$199.32	12.118%	$223.4736	$223.47	$223.45	$223.50
Purchase #7	$207.28	12.565%	$233.3247	$233.32	$233.30	$233.30
7 purchase totals =	$951.41		$1,049.6808	$1,049.68	$1,049.65	$1,049.60