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	$164.52	12.825%	$185.6197	$185.62	$185.60	$185.60
Purchase #2	$229.52	3.809%	$238.2624	$238.26	$238.25	$238.30
Purchase #3	$204.61	5.496%	$215.8554	$215.86	$215.85	$215.90
Purchase #4	$193.45	8.780%	$210.4349	$210.43	$210.45	$210.40
Purchase #5	$116.45	13.276%	$131.9099	$131.91	$131.90	$131.90
Purchase #6	$178.84	13.562%	$203.0943	$203.09	$203.10	$203.10
Purchase #7	$38.86	8.308%	$42.0885	$42.09	$42.10	$42.10
7 purchase totals =	$1,126.25		$1,227.2651	$1,227.26	$1,227.25	$1,227.30