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	$81.71	8.276%	$88.4723	$88.47	$88.45	$88.50
Purchase #2	$223.51	12.686%	$251.8645	$251.86	$251.85	$251.90
Purchase #3	$225.96	5.724%	$238.894	$238.89	$238.90	$238.90
Purchase #4	$185.59	6.104%	$196.9184	$196.92	$196.90	$196.90
Purchase #5	$25.97	7.705%	$27.971	$27.97	$27.95	$28.00
Purchase #6	$47.76	10.754%	$52.8961	$52.90	$52.90	$52.90
Purchase #7	$148.48	8.323%	$160.838	$160.84	$160.85	$160.80
7 purchase totals =	$938.98		$1,017.8543	$1,017.85	$1,017.80	$1,017.90