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	$39.49	4.861%	$41.4096	$41.41	$41.40	$41.40
Purchase #2	$57.26	6.849%	$61.1817	$61.18	$61.20	$61.20
Purchase #3	$137.41	11.293%	$152.9277	$152.93	$152.95	$152.90
Purchase #4	$41.84	12.873%	$47.2261	$47.23	$47.25	$47.20
Purchase #5	$64.81	12.247%	$72.7473	$72.75	$72.75	$72.70
Purchase #6	$240.80	4.211%	$250.9401	$250.94	$250.95	$250.90
Purchase #7	$92.68	13.146%	$104.8637	$104.86	$104.85	$104.90
7 purchase totals =	$674.29		$731.2962	$731.30	$731.35	$731.20