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	$96.48	13.818%	$109.8116	$109.81	$109.80	$109.80
Purchase #2	$116.86	10.297%	$128.8931	$128.89	$128.90	$128.90
Purchase #3	$109.38	7.790%	$117.9007	$117.90	$117.90	$117.90
Purchase #4	$203.59	7.266%	$218.3828	$218.38	$218.40	$218.40
Purchase #5	$80.36	10.163%	$88.527	$88.53	$88.55	$88.50
Purchase #6	$164.46	7.251%	$176.385	$176.39	$176.40	$176.40
Purchase #7	$43.47	8.704%	$47.2536	$47.25	$47.25	$47.30
7 purchase totals =	$814.60		$887.1538	$887.15	$887.20	$887.20