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	$164.89	4.465%	$172.2523	$172.25	$172.25	$172.30
Purchase #2	$171.73	10.725%	$190.148	$190.15	$190.15	$190.10
Purchase #3	$179.79	12.846%	$202.8858	$202.89	$202.90	$202.90
Purchase #4	$197.66	5.581%	$208.6914	$208.69	$208.70	$208.70
Purchase #5	$79.52	7.449%	$85.4434	$85.44	$85.45	$85.40
Purchase #6	$101.32	13.321%	$114.8168	$114.82	$114.80	$114.80
Purchase #7	$155.90	7.209%	$167.1388	$167.14	$167.15	$167.10
7 purchase totals =	$1,050.81		$1,141.3765	$1,141.38	$1,141.40	$1,141.30