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	$217.77	7.264%	$233.5888	$233.59	$233.60	$233.60
Purchase #2	$187.76	4.750%	$196.6786	$196.68	$196.70	$196.70
Purchase #3	$61.45	11.235%	$68.3539	$68.35	$68.35	$68.40
Purchase #4	$250.89	9.640%	$275.0758	$275.08	$275.10	$275.10
Purchase #5	$191.67	9.766%	$210.3885	$210.39	$210.40	$210.40
Purchase #6	$9.98	13.166%	$11.294	$11.29	$11.30	$11.30
Purchase #7	$72.29	8.512%	$78.4433	$78.44	$78.45	$78.40
7 purchase totals =	$991.81		$1,073.8229	$1,073.82	$1,073.90	$1,073.90