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	$65.29	12.147%	$73.2208	$73.22	$73.20	$73.20
Purchase #2	$26.39	4.508%	$27.5797	$27.58	$27.60	$27.60
Purchase #3	$152.56	11.705%	$170.4171	$170.42	$170.40	$170.40
Purchase #4	$27.48	13.845%	$31.2846	$31.28	$31.30	$31.30
Purchase #5	$104.78	6.821%	$111.927	$111.93	$111.95	$111.90
Purchase #6	$68.88	6.135%	$73.1058	$73.11	$73.10	$73.10
Purchase #7	$180.86	7.525%	$194.4697	$194.47	$194.45	$194.50
7 purchase totals =	$626.24		$682.0047	$682.01	$682.00	$682.00