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	$247.58	6.767%	$264.3337	$264.33	$264.35	$264.30
Purchase #2	$106.74	4.138%	$111.1569	$111.16	$111.15	$111.20
Purchase #3	$191.51	10.121%	$210.8927	$210.89	$210.90	$210.90
Purchase #4	$22.61	4.269%	$23.5752	$23.58	$23.60	$23.60
Purchase #5	$92.60	13.853%	$105.4279	$105.43	$105.45	$105.40
Purchase #6	$61.80	12.247%	$69.3686	$69.37	$69.35	$69.40
Purchase #7	$199.88	12.337%	$224.5392	$224.54	$224.55	$224.50
7 purchase totals =	$922.72		$1,009.2942	$1,009.30	$1,009.35	$1,009.30