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	$131.75	11.637%	$147.0817	$147.08	$147.10	$147.10
Purchase #2	$12.54	13.524%	$14.2359	$14.24	$14.25	$14.20
Purchase #3	$79.43	12.341%	$89.2325	$89.23	$89.25	$89.20
Purchase #4	$126.99	3.559%	$131.5096	$131.51	$131.50	$131.50
Purchase #5	$18.90	9.750%	$20.7428	$20.74	$20.75	$20.70
Purchase #6	$147.39	7.673%	$158.6992	$158.70	$158.70	$158.70
Purchase #7	$139.60	10.185%	$153.8183	$153.82	$153.80	$153.80
7 purchase totals =	$656.60		$715.3200	$715.32	$715.35	$715.20