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	$250.57	4.213%	$261.1265	$261.13	$261.15	$261.10
Purchase #2	$198.54	3.542%	$205.5723	$205.57	$205.55	$205.60
Purchase #3	$56.57	4.466%	$59.0964	$59.10	$59.10	$59.10
Purchase #4	$79.44	8.164%	$85.9255	$85.93	$85.95	$85.90
Purchase #5	$183.50	3.613%	$190.1299	$190.13	$190.15	$190.10
Purchase #6	$160.36	3.262%	$165.5909	$165.59	$165.60	$165.60
Purchase #7	$214.77	7.664%	$231.23	$231.23	$231.25	$231.20
7 purchase totals =	$1,143.75		$1,198.6715	$1,198.68	$1,198.75	$1,198.60