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	$153.29	7.532%	$164.8358	$164.84	$164.85	$164.80
Purchase #2	$90.65	9.555%	$99.3116	$99.31	$99.30	$99.30
Purchase #3	$39.26	6.874%	$41.9587	$41.96	$41.95	$42.00
Purchase #4	$12.93	11.444%	$14.4097	$14.41	$14.40	$14.40
Purchase #5	$14.39	10.784%	$15.9418	$15.94	$15.95	$15.90
Purchase #6	$99.86	9.817%	$109.6633	$109.66	$109.65	$109.70
Purchase #7	$18.43	7.209%	$19.7586	$19.76	$19.75	$19.80
7 purchase totals =	$428.81		$465.8795	$465.88	$465.85	$465.90