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	$226.27	10.656%	$250.3813	$250.38	$250.40	$250.40
Purchase #2	$163.89	9.414%	$179.3186	$179.32	$179.30	$179.30
Purchase #3	$54.55	3.408%	$56.4091	$56.41	$56.40	$56.40
Purchase #4	$186.98	11.716%	$208.8866	$208.89	$208.90	$208.90
Purchase #5	$208.92	7.336%	$224.2464	$224.25	$224.25	$224.20
Purchase #6	$179.86	11.553%	$200.6392	$200.64	$200.65	$200.60
Purchase #7	$31.84	9.747%	$34.9434	$34.94	$34.95	$34.90
7 purchase totals =	$1,052.31		$1,154.8246	$1,154.83	$1,154.85	$1,154.70