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	$164.31	9.218%	$179.4561	$179.46	$179.45	$179.50
Purchase #2	$78.91	4.178%	$82.2069	$82.21	$82.20	$82.20
Purchase #3	$234.96	3.758%	$243.7898	$243.79	$243.80	$243.80
Purchase #4	$35.26	5.311%	$37.1327	$37.13	$37.15	$37.10
Purchase #5	$12.57	6.380%	$13.372	$13.37	$13.35	$13.40
Purchase #6	$249.58	13.322%	$282.829	$282.83	$282.85	$282.80
Purchase #7	$188.98	4.613%	$197.6976	$197.70	$197.70	$197.70
7 purchase totals =	$964.57		$1,036.4841	$1,036.49	$1,036.50	$1,036.50