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	$205.49	7.697%	$221.3066	$221.31	$221.30	$221.30
Purchase #2	$47.66	10.276%	$52.5575	$52.56	$52.55	$52.60
Purchase #3	$30.30	7.777%	$32.6564	$32.66	$32.65	$32.70
Purchase #4	$241.77	3.187%	$249.4752	$249.48	$249.50	$249.50
Purchase #5	$202.31	3.127%	$208.6362	$208.64	$208.65	$208.60
Purchase #6	$191.34	10.663%	$211.7426	$211.74	$211.75	$211.70
Purchase #7	$212.83	5.488%	$224.5101	$224.51	$224.50	$224.50
7 purchase totals =	$1,131.70		$1,200.8846	$1,200.90	$1,200.90	$1,200.90