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	$174.66	4.731%	$182.9232	$182.92	$182.90	$182.90
Purchase #2	$79.45	11.153%	$88.3111	$88.31	$88.30	$88.30
Purchase #3	$168.83	6.662%	$180.0775	$180.08	$180.10	$180.10
Purchase #4	$89.65	10.789%	$99.3223	$99.32	$99.30	$99.30
Purchase #5	$47.82	8.679%	$51.9703	$51.97	$51.95	$52.00
Purchase #6	$229.63	11.622%	$256.3176	$256.32	$256.30	$256.30
Purchase #7	$150.90	11.818%	$168.7334	$168.73	$168.75	$168.70
7 purchase totals =	$940.94		$1,027.6554	$1,027.65	$1,027.60	$1,027.60