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	$117.44	8.160%	$127.0231	$127.02	$127.00	$127.00
Purchase #2	$131.64	10.860%	$145.9361	$145.94	$145.95	$145.90
Purchase #3	$71.92	10.564%	$79.5176	$79.52	$79.50	$79.50
Purchase #4	$209.62	13.802%	$238.5518	$238.55	$238.55	$238.60
Purchase #5	$53.52	12.795%	$60.3679	$60.37	$60.35	$60.40
Purchase #6	$153.43	7.314%	$164.6519	$164.65	$164.65	$164.70
Purchase #7	$198.43	7.281%	$212.8777	$212.88	$212.90	$212.90
7 purchase totals =	$936.00		$1,028.9261	$1,028.93	$1,028.90	$1,029.00