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	$90.85	6.702%	$96.9388	$96.94	$96.95	$96.90
Purchase #2	$190.99	3.119%	$196.947	$196.95	$196.95	$196.90
Purchase #3	$75.57	12.657%	$85.1349	$85.13	$85.15	$85.10
Purchase #4	$172.34	11.149%	$191.5542	$191.55	$191.55	$191.60
Purchase #5	$78.92	5.247%	$83.0609	$83.06	$83.05	$83.10
Purchase #6	$142.48	4.563%	$148.9814	$148.98	$149.00	$149.00
Purchase #7	$228.51	4.650%	$239.1357	$239.14	$239.15	$239.10
7 purchase totals =	$979.66		$1,041.7529	$1,041.75	$1,041.80	$1,041.70