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	$52.57	13.112%	$59.463	$59.46	$59.45	$59.50
Purchase #2	$150.40	9.462%	$164.6308	$164.63	$164.65	$164.60
Purchase #3	$141.68	6.305%	$150.6129	$150.61	$150.60	$150.60
Purchase #4	$186.81	3.318%	$193.0084	$193.01	$193.00	$193.00
Purchase #5	$207.56	10.779%	$229.9329	$229.93	$229.95	$229.90
Purchase #6	$230.41	3.430%	$238.3131	$238.31	$238.30	$238.30
Purchase #7	$114.88	7.481%	$123.4742	$123.47	$123.45	$123.50
7 purchase totals =	$1,084.31		$1,159.4353	$1,159.42	$1,159.40	$1,159.40