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	$148.84	10.832%	$164.9623	$164.96	$164.95	$165.00
Purchase #2	$127.87	3.515%	$132.3646	$132.36	$132.35	$132.40
Purchase #3	$231.38	10.702%	$256.1423	$256.14	$256.15	$256.10
Purchase #4	$246.39	4.676%	$257.9112	$257.91	$257.90	$257.90
Purchase #5	$99.78	9.444%	$109.2032	$109.20	$109.20	$109.20
Purchase #6	$53.67	11.608%	$59.9	$59.90	$59.90	$59.90
Purchase #7	$208.54	3.367%	$215.5615	$215.56	$215.55	$215.60
7 purchase totals =	$1,116.47		$1,196.0451	$1,196.03	$1,196.00	$1,196.10