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	$218.43	11.154%	$242.7937	$242.79	$242.80	$242.80
Purchase #2	$78.76	12.444%	$88.5609	$88.56	$88.55	$88.60
Purchase #3	$158.34	13.485%	$179.6921	$179.69	$179.70	$179.70
Purchase #4	$100.78	13.321%	$114.2049	$114.20	$114.20	$114.20
Purchase #5	$60.83	4.540%	$63.5917	$63.59	$63.60	$63.60
Purchase #6	$242.84	12.654%	$273.569	$273.57	$273.55	$273.60
Purchase #7	$34.56	12.526%	$38.889	$38.89	$38.90	$38.90
7 purchase totals =	$894.54		$1,001.3013	$1,001.29	$1,001.30	$1,001.40