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	$137.70	4.506%	$143.9048	$143.90	$143.90	$143.90
Purchase #2	$235.88	3.250%	$243.5461	$243.55	$243.55	$243.50
Purchase #3	$155.37	3.342%	$160.5625	$160.56	$160.55	$160.60
Purchase #4	$57.78	8.658%	$62.7826	$62.78	$62.80	$62.80
Purchase #5	$200.99	7.142%	$215.3447	$215.34	$215.35	$215.30
Purchase #6	$177.67	6.151%	$188.5985	$188.60	$188.60	$188.60
Purchase #7	$48.88	9.223%	$53.3882	$53.39	$53.40	$53.40
7 purchase totals =	$1,014.27		$1,068.1274	$1,068.12	$1,068.15	$1,068.10