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	$143.34	13.104%	$162.1233	$162.12	$162.10	$162.10
Purchase #2	$54.41	6.433%	$57.9102	$57.91	$57.90	$57.90
Purchase #3	$208.45	8.162%	$225.4637	$225.46	$225.45	$225.50
Purchase #4	$123.54	13.864%	$140.6676	$140.67	$140.65	$140.70
Purchase #5	$88.46	3.564%	$91.6127	$91.61	$91.60	$91.60
Purchase #6	$229.36	5.549%	$242.0872	$242.09	$242.10	$242.10
Purchase #7	$156.45	6.542%	$166.685	$166.69	$166.70	$166.70
7 purchase totals =	$1,004.01		$1,086.5497	$1,086.55	$1,086.50	$1,086.60