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	$167.62	10.147%	$184.6284	$184.63	$184.65	$184.60
Purchase #2	$37.96	6.326%	$40.3613	$40.36	$40.35	$40.40
Purchase #3	$229.44	9.251%	$250.6655	$250.67	$250.65	$250.70
Purchase #4	$113.38	4.853%	$118.8823	$118.88	$118.90	$118.90
Purchase #5	$75.90	3.149%	$78.2901	$78.29	$78.30	$78.30
Purchase #6	$75.93	8.532%	$82.4083	$82.41	$82.40	$82.40
Purchase #7	$16.47	9.440%	$18.0248	$18.02	$18.00	$18.00
7 purchase totals =	$716.70		$773.2607	$773.26	$773.25	$773.30