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	$170.62	8.790%	$185.6175	$185.62	$185.60	$185.60
Purchase #2	$87.33	3.604%	$90.4774	$90.48	$90.50	$90.50
Purchase #3	$29.43	8.109%	$31.8165	$31.82	$31.80	$31.80
Purchase #4	$149.82	11.253%	$166.6792	$166.68	$166.70	$166.70
Purchase #5	$132.97	7.871%	$143.4361	$143.44	$143.45	$143.40
Purchase #6	$168.25	7.532%	$180.9226	$180.92	$180.90	$180.90
Purchase #7	$195.83	4.732%	$205.0967	$205.10	$205.10	$205.10
7 purchase totals =	$934.25		$1,004.0460	$1,004.06	$1,004.05	$1,004.00