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	$144.38	5.593%	$152.4552	$152.46	$152.45	$152.50
Purchase #2	$16.63	10.605%	$18.3936	$18.39	$18.40	$18.40
Purchase #3	$94.37	7.125%	$101.0939	$101.09	$101.10	$101.10
Purchase #4	$11.57	6.402%	$12.3107	$12.31	$12.30	$12.30
Purchase #5	$83.97	6.588%	$89.5019	$89.50	$89.50	$89.50
Purchase #6	$17.98	13.668%	$20.4375	$20.44	$20.45	$20.40
Purchase #7	$106.32	12.447%	$119.5537	$119.55	$119.55	$119.60
7 purchase totals =	$475.22		$513.7465	$513.74	$513.75	$513.80