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	$152.83	9.511%	$167.3657	$167.37	$167.35	$167.40
Purchase #2	$193.93	12.692%	$218.5436	$218.54	$218.55	$218.50
Purchase #3	$79.42	4.621%	$83.09	$83.09	$83.10	$83.10
Purchase #4	$69.78	12.250%	$78.3281	$78.33	$78.35	$78.30
Purchase #5	$36.84	8.581%	$40.0012	$40.00	$40.00	$40.00
Purchase #6	$11.95	3.144%	$12.3257	$12.33	$12.35	$12.30
Purchase #7	$192.79	12.572%	$217.0276	$217.03	$217.05	$217.00
7 purchase totals =	$737.54		$816.6819	$816.69	$816.75	$816.60