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	$84.58	6.518%	$90.0929	$90.09	$90.10	$90.10
Purchase #2	$133.67	10.209%	$147.3164	$147.32	$147.30	$147.30
Purchase #3	$151.86	9.317%	$166.0088	$166.01	$166.00	$166.00
Purchase #4	$240.88	10.753%	$266.7818	$266.78	$266.80	$266.80
Purchase #5	$190.94	3.134%	$196.9241	$196.92	$196.90	$196.90
Purchase #6	$193.98	3.599%	$200.9613	$200.96	$200.95	$201.00
Purchase #7	$73.66	6.104%	$78.1562	$78.16	$78.15	$78.20
7 purchase totals =	$1,069.57		$1,146.2415	$1,146.24	$1,146.20	$1,146.30