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	$138.81	10.588%	$153.5072	$153.51	$153.50	$153.50
Purchase #2	$127.29	11.494%	$141.9207	$141.92	$141.90	$141.90
Purchase #3	$151.87	9.116%	$165.7145	$165.71	$165.70	$165.70
Purchase #4	$190.62	10.544%	$210.719	$210.72	$210.70	$210.70
Purchase #5	$194.37	11.768%	$217.2435	$217.24	$217.25	$217.20
Purchase #6	$41.76	3.646%	$43.2826	$43.28	$43.30	$43.30
Purchase #7	$95.76	11.760%	$107.0214	$107.02	$107.00	$107.00
7 purchase totals =	$940.48		$1,039.4089	$1,039.40	$1,039.35	$1,039.30