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	$60.50	13.683%	$68.7782	$68.78	$68.80	$68.80
Purchase #2	$35.88	5.320%	$37.7888	$37.79	$37.80	$37.80
Purchase #3	$142.59	6.795%	$152.279	$152.28	$152.30	$152.30
Purchase #4	$54.64	9.146%	$59.6374	$59.64	$59.65	$59.60
Purchase #5	$159.83	7.127%	$171.2211	$171.22	$171.20	$171.20
Purchase #6	$43.46	4.282%	$45.321	$45.32	$45.30	$45.30
Purchase #7	$183.74	12.463%	$206.6395	$206.64	$206.65	$206.60
7 purchase totals =	$680.64		$741.6650	$741.67	$741.70	$741.60