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	$206.89	4.451%	$216.0987	$216.10	$216.10	$216.10
Purchase #2	$65.37	3.760%	$67.8279	$67.83	$67.85	$67.80
Purchase #3	$249.89	3.741%	$259.2384	$259.24	$259.25	$259.20
Purchase #4	$142.88	6.482%	$152.1415	$152.14	$152.15	$152.10
Purchase #5	$142.70	5.632%	$150.7369	$150.74	$150.75	$150.70
Purchase #6	$158.68	6.134%	$168.4134	$168.41	$168.40	$168.40
Purchase #7	$39.44	13.820%	$44.8906	$44.89	$44.90	$44.90
7 purchase totals =	$1,005.85		$1,059.3474	$1,059.35	$1,059.40	$1,059.20