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	$134.83	13.826%	$153.4716	$153.47	$153.45	$153.50
Purchase #2	$55.87	6.206%	$59.3373	$59.34	$59.35	$59.30
Purchase #3	$63.41	7.150%	$67.9438	$67.94	$67.95	$67.90
Purchase #4	$148.74	9.444%	$162.787	$162.79	$162.80	$162.80
Purchase #5	$47.57	7.502%	$51.1387	$51.14	$51.15	$51.10
Purchase #6	$150.41	9.308%	$164.4102	$164.41	$164.40	$164.40
Purchase #7	$94.65	3.445%	$97.9107	$97.91	$97.90	$97.90
7 purchase totals =	$695.48		$756.9993	$757.00	$757.00	$756.90