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	$163.47	13.687%	$185.8441	$185.84	$185.85	$185.80
Purchase #2	$26.37	9.445%	$28.8606	$28.86	$28.85	$28.90
Purchase #3	$74.90	4.638%	$78.3739	$78.37	$78.35	$78.40
Purchase #4	$84.30	5.354%	$88.8134	$88.81	$88.80	$88.80
Purchase #5	$69.39	4.165%	$72.2801	$72.28	$72.30	$72.30
Purchase #6	$238.45	10.831%	$264.2765	$264.28	$264.30	$264.30
Purchase #7	$78.80	4.374%	$82.2467	$82.25	$82.25	$82.20
7 purchase totals =	$735.68		$800.6953	$800.69	$800.70	$800.70