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	$114.40	4.121%	$119.1144	$119.11	$119.10	$119.10
Purchase #2	$43.34	5.232%	$45.6075	$45.61	$45.60	$45.60
Purchase #3	$125.57	12.536%	$141.3115	$141.31	$141.30	$141.30
Purchase #4	$196.87	13.557%	$223.5597	$223.56	$223.55	$223.60
Purchase #5	$52.62	13.502%	$59.7248	$59.72	$59.70	$59.70
Purchase #6	$195.32	12.832%	$220.3835	$220.38	$220.40	$220.40
Purchase #7	$70.81	10.265%	$78.0786	$78.08	$78.10	$78.10
7 purchase totals =	$798.93		$887.7800	$887.77	$887.75	$887.80