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	$38.25	13.528%	$43.4245	$43.42	$43.40	$43.40
Purchase #2	$147.56	6.543%	$157.2149	$157.21	$157.20	$157.20
Purchase #3	$31.92	4.853%	$33.4691	$33.47	$33.45	$33.50
Purchase #4	$49.74	6.664%	$53.0547	$53.05	$53.05	$53.10
Purchase #5	$97.44	5.617%	$102.9132	$102.91	$102.90	$102.90
Purchase #6	$197.80	12.283%	$222.0958	$222.10	$222.10	$222.10
Purchase #7	$166.41	3.797%	$172.7286	$172.73	$172.75	$172.70
7 purchase totals =	$729.12		$784.9008	$784.89	$784.85	$784.90