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	$60.54	5.637%	$63.9526	$63.95	$63.95	$64.00
Purchase #2	$36.53	12.192%	$40.9837	$40.98	$41.00	$41.00
Purchase #3	$68.40	5.627%	$72.2489	$72.25	$72.25	$72.20
Purchase #4	$48.65	12.538%	$54.7497	$54.75	$54.75	$54.70
Purchase #5	$46.97	11.133%	$52.1992	$52.20	$52.20	$52.20
Purchase #6	$86.35	4.576%	$90.3014	$90.30	$90.30	$90.30
Purchase #7	$114.26	12.437%	$128.4705	$128.47	$128.45	$128.50
7 purchase totals =	$461.70		$502.9060	$502.90	$502.90	$502.90