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	$214.98	10.758%	$238.1075	$238.11	$238.10	$238.10
Purchase #2	$147.92	9.821%	$162.4472	$162.45	$162.45	$162.40
Purchase #3	$57.61	12.709%	$64.9317	$64.93	$64.95	$64.90
Purchase #4	$160.86	7.441%	$172.8296	$172.83	$172.85	$172.80
Purchase #5	$91.83	9.787%	$100.8174	$100.82	$100.80	$100.80
Purchase #6	$68.25	5.591%	$72.0659	$72.07	$72.05	$72.10
Purchase #7	$219.91	4.592%	$230.0083	$230.01	$230.00	$230.00
7 purchase totals =	$961.36		$1,041.2076	$1,041.22	$1,041.20	$1,041.10