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	$137.66	13.663%	$156.4685	$156.47	$156.45	$156.50
Purchase #2	$102.58	4.684%	$107.3848	$107.38	$107.40	$107.40
Purchase #3	$73.46	6.662%	$78.3539	$78.35	$78.35	$78.40
Purchase #4	$240.30	13.724%	$273.2788	$273.28	$273.30	$273.30
Purchase #5	$198.78	12.328%	$223.2856	$223.29	$223.30	$223.30
Purchase #6	$201.68	10.154%	$222.1586	$222.16	$222.15	$222.20
Purchase #7	$195.86	10.363%	$216.157	$216.16	$216.15	$216.20
7 purchase totals =	$1,150.32		$1,277.0872	$1,277.09	$1,277.10	$1,277.30