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	$187.51	11.185%	$208.483	$208.48	$208.50	$208.50
Purchase #2	$82.97	8.407%	$89.9453	$89.95	$89.95	$89.90
Purchase #3	$249.81	8.207%	$270.3119	$270.31	$270.30	$270.30
Purchase #4	$47.81	10.707%	$52.929	$52.93	$52.95	$52.90
Purchase #5	$232.81	9.128%	$254.0609	$254.06	$254.05	$254.10
Purchase #6	$38.92	4.635%	$40.7239	$40.72	$40.70	$40.70
Purchase #7	$203.91	5.576%	$215.28	$215.28	$215.30	$215.30
7 purchase totals =	$1,043.74		$1,131.7340	$1,131.73	$1,131.75	$1,131.70