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	$86.71	10.870%	$96.1354	$96.14	$96.15	$96.10
Purchase #2	$188.41	8.873%	$205.1276	$205.13	$205.15	$205.10
Purchase #3	$24.58	10.789%	$27.2319	$27.23	$27.25	$27.20
Purchase #4	$131.39	10.532%	$145.228	$145.23	$145.25	$145.20
Purchase #5	$7.65	3.744%	$7.9364	$7.94	$7.95	$7.90
Purchase #6	$84.89	4.675%	$88.8586	$88.86	$88.85	$88.90
Purchase #7	$171.79	10.297%	$189.4792	$189.48	$189.50	$189.50
7 purchase totals =	$695.42		$759.9971	$760.01	$760.10	$759.90