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	$176.65	4.515%	$184.6257	$184.63	$184.65	$184.60
Purchase #2	$99.38	6.349%	$105.6896	$105.69	$105.70	$105.70
Purchase #3	$89.53	13.409%	$101.5351	$101.54	$101.55	$101.50
Purchase #4	$100.96	3.210%	$104.2008	$104.20	$104.20	$104.20
Purchase #5	$167.81	11.497%	$187.1031	$187.10	$187.10	$187.10
Purchase #6	$129.63	7.499%	$139.351	$139.35	$139.35	$139.40
Purchase #7	$214.29	13.847%	$243.9627	$243.96	$243.95	$244.00
7 purchase totals =	$978.25		$1,066.4680	$1,066.47	$1,066.50	$1,066.50