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	$176.38	3.586%	$182.705	$182.71	$182.70	$182.70
Purchase #2	$172.58	13.836%	$196.4582	$196.46	$196.45	$196.50
Purchase #3	$108.75	10.834%	$120.532	$120.53	$120.55	$120.50
Purchase #4	$143.32	12.405%	$161.0988	$161.10	$161.10	$161.10
Purchase #5	$30.29	9.303%	$33.1079	$33.11	$33.10	$33.10
Purchase #6	$53.45	13.392%	$60.608	$60.61	$60.60	$60.60
Purchase #7	$90.78	4.211%	$94.6027	$94.60	$94.60	$94.60
7 purchase totals =	$775.55		$849.1126	$849.12	$849.10	$849.10