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	$148.44	11.365%	$165.3102	$165.31	$165.30	$165.30
Purchase #2	$180.61	9.408%	$197.6018	$197.60	$197.60	$197.60
Purchase #3	$37.69	8.555%	$40.9144	$40.91	$40.90	$40.90
Purchase #4	$82.49	3.585%	$85.4473	$85.45	$85.45	$85.40
Purchase #5	$145.31	13.250%	$164.5636	$164.56	$164.55	$164.60
Purchase #6	$215.80	11.149%	$239.8595	$239.86	$239.85	$239.90
Purchase #7	$193.67	10.811%	$214.6077	$214.61	$214.60	$214.60
7 purchase totals =	$1,004.01		$1,108.3045	$1,108.30	$1,108.25	$1,108.30