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	$167.25	10.283%	$184.4483	$184.45	$184.45	$184.40
Purchase #2	$101.62	13.117%	$114.9495	$114.95	$114.95	$114.90
Purchase #3	$84.33	8.562%	$91.5503	$91.55	$91.55	$91.60
Purchase #4	$86.40	3.390%	$89.329	$89.33	$89.35	$89.30
Purchase #5	$118.46	4.626%	$123.94	$123.94	$123.95	$123.90
Purchase #6	$43.66	3.647%	$45.2523	$45.25	$45.25	$45.30
Purchase #7	$161.99	7.544%	$174.2105	$174.21	$174.20	$174.20
7 purchase totals =	$763.71		$823.6799	$823.68	$823.70	$823.60