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	$30.71	10.556%	$33.9517	$33.95	$33.95	$34.00
Purchase #2	$15.43	3.152%	$15.9164	$15.92	$15.90	$15.90
Purchase #3	$78.88	10.164%	$86.8974	$86.90	$86.90	$86.90
Purchase #4	$158.92	8.399%	$172.2677	$172.27	$172.25	$172.30
Purchase #5	$7.88	8.390%	$8.5411	$8.54	$8.55	$8.50
Purchase #6	$125.44	13.185%	$141.9793	$141.98	$142.00	$142.00
Purchase #7	$89.36	12.463%	$100.4969	$100.50	$100.50	$100.50
7 purchase totals =	$506.62		$560.0505	$560.06	$560.05	$560.10