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	$133.61	5.818%	$141.3834	$141.38	$141.40	$141.40
Purchase #2	$195.28	12.386%	$219.4674	$219.47	$219.45	$219.50
Purchase #3	$28.48	9.354%	$31.144	$31.14	$31.15	$31.10
Purchase #4	$109.59	4.807%	$114.858	$114.86	$114.85	$114.90
Purchase #5	$175.99	9.367%	$192.475	$192.48	$192.50	$192.50
Purchase #6	$79.25	5.401%	$83.5303	$83.53	$83.55	$83.50
Purchase #7	$233.31	3.261%	$240.9182	$240.92	$240.90	$240.90
7 purchase totals =	$955.51		$1,023.7763	$1,023.78	$1,023.80	$1,023.80