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	$45.66	5.452%	$48.1494	$48.15	$48.15	$48.10
Purchase #2	$79.61	3.403%	$82.3191	$82.32	$82.30	$82.30
Purchase #3	$25.96	6.421%	$27.6269	$27.63	$27.65	$27.60
Purchase #4	$29.63	7.593%	$31.8798	$31.88	$31.90	$31.90
Purchase #5	$225.98	12.102%	$253.3281	$253.33	$253.35	$253.30
Purchase #6	$146.78	6.716%	$156.6377	$156.64	$156.65	$156.60
Purchase #7	$178.30	3.652%	$184.8115	$184.81	$184.80	$184.80
7 purchase totals =	$731.92		$784.7525	$784.76	$784.80	$784.60