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	$67.94	7.228%	$72.8507	$72.85	$72.85	$72.90
Purchase #2	$195.84	10.620%	$216.6382	$216.64	$216.65	$216.60
Purchase #3	$55.41	4.221%	$57.7489	$57.75	$57.75	$57.70
Purchase #4	$183.88	6.773%	$196.3342	$196.33	$196.35	$196.30
Purchase #5	$168.36	6.201%	$178.8	$178.80	$178.80	$178.80
Purchase #6	$214.40	12.580%	$241.3715	$241.37	$241.35	$241.40
Purchase #7	$15.32	7.847%	$16.5222	$16.52	$16.50	$16.50
7 purchase totals =	$901.15		$980.2657	$980.26	$980.25	$980.20