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	$111.94	3.528%	$115.8892	$115.89	$115.90	$115.90
Purchase #2	$218.97	5.121%	$230.1835	$230.18	$230.20	$230.20
Purchase #3	$75.63	4.365%	$78.9312	$78.93	$78.95	$78.90
Purchase #4	$68.75	5.266%	$72.3704	$72.37	$72.35	$72.40
Purchase #5	$223.70	7.707%	$240.9406	$240.94	$240.95	$240.90
Purchase #6	$156.52	5.278%	$164.7811	$164.78	$164.80	$164.80
Purchase #7	$231.92	4.482%	$242.3147	$242.31	$242.30	$242.30
7 purchase totals =	$1,087.43		$1,145.4107	$1,145.40	$1,145.45	$1,145.40