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	$239.83	10.199%	$264.2903	$264.29	$264.30	$264.30
Purchase #2	$182.55	12.279%	$204.9653	$204.97	$204.95	$205.00
Purchase #3	$137.43	5.521%	$145.0175	$145.02	$145.00	$145.00
Purchase #4	$196.29	11.411%	$218.6887	$218.69	$218.70	$218.70
Purchase #5	$131.41	12.112%	$147.3264	$147.33	$147.35	$147.30
Purchase #6	$40.55	13.111%	$45.8665	$45.87	$45.85	$45.90
Purchase #7	$75.67	3.688%	$78.4607	$78.46	$78.45	$78.50
7 purchase totals =	$1,003.73		$1,104.6154	$1,104.63	$1,104.60	$1,104.70