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	$232.51	13.799%	$264.5941	$264.59	$264.60	$264.60
Purchase #2	$231.81	4.722%	$242.7561	$242.76	$242.75	$242.80
Purchase #3	$26.25	3.286%	$27.1126	$27.11	$27.10	$27.10
Purchase #4	$72.73	13.749%	$82.7296	$82.73	$82.75	$82.70
Purchase #5	$45.34	9.460%	$49.6292	$49.63	$49.65	$49.60
Purchase #6	$240.72	3.423%	$248.9598	$248.96	$248.95	$249.00
Purchase #7	$128.82	11.671%	$143.8546	$143.85	$143.85	$143.90
7 purchase totals =	$978.18		$1,059.6360	$1,059.63	$1,059.65	$1,059.70