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	$235.69	13.783%	$268.1752	$268.18	$268.20	$268.20
Purchase #2	$33.48	13.525%	$38.0082	$38.01	$38.00	$38.00
Purchase #3	$82.61	9.317%	$90.3068	$90.31	$90.30	$90.30
Purchase #4	$92.64	11.468%	$103.264	$103.26	$103.25	$103.30
Purchase #5	$240.75	7.141%	$257.942	$257.94	$257.95	$257.90
Purchase #6	$202.29	4.162%	$210.7093	$210.71	$210.70	$210.70
Purchase #7	$50.55	5.671%	$53.4167	$53.42	$53.40	$53.40
7 purchase totals =	$938.01		$1,021.8222	$1,021.83	$1,021.80	$1,021.80