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	$167.49	7.127%	$179.427	$179.43	$179.45	$179.40
Purchase #2	$94.57	7.401%	$101.5691	$101.57	$101.55	$101.60
Purchase #3	$96.60	7.516%	$103.8605	$103.86	$103.85	$103.90
Purchase #4	$230.77	7.446%	$247.9531	$247.95	$247.95	$248.00
Purchase #5	$72.38	7.800%	$78.0256	$78.03	$78.05	$78.00
Purchase #6	$103.52	12.199%	$116.1484	$116.15	$116.15	$116.10
Purchase #7	$74.65	12.476%	$83.9633	$83.96	$83.95	$84.00
7 purchase totals =	$839.98		$910.9470	$910.95	$910.95	$911.00