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	$214.54	13.158%	$242.7692	$242.77	$242.75	$242.80
Purchase #2	$163.38	11.586%	$182.3092	$182.31	$182.30	$182.30
Purchase #3	$61.34	3.729%	$63.6274	$63.63	$63.65	$63.60
Purchase #4	$147.36	12.384%	$165.6091	$165.61	$165.60	$165.60
Purchase #5	$88.71	4.175%	$92.4136	$92.41	$92.40	$92.40
Purchase #6	$82.98	7.863%	$89.5047	$89.50	$89.50	$89.50
Purchase #7	$84.69	7.817%	$91.3102	$91.31	$91.30	$91.30
7 purchase totals =	$843.00		$927.5434	$927.54	$927.50	$927.50