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	$177.63	13.864%	$202.2566	$202.26	$202.25	$202.30
Purchase #2	$118.48	10.716%	$131.1763	$131.18	$131.20	$131.20
Purchase #3	$50.32	10.340%	$55.5231	$55.52	$55.50	$55.50
Purchase #4	$15.89	13.772%	$18.0784	$18.08	$18.10	$18.10
Purchase #5	$55.55	6.623%	$59.2291	$59.23	$59.25	$59.20
Purchase #6	$186.31	9.567%	$204.1343	$204.13	$204.15	$204.10
Purchase #7	$135.68	13.594%	$154.1243	$154.12	$154.10	$154.10
7 purchase totals =	$739.86		$824.5221	$824.52	$824.55	$824.50