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	$59.53	9.685%	$65.2955	$65.30	$65.30	$65.30
Purchase #2	$167.95	5.257%	$176.7791	$176.78	$176.80	$176.80
Purchase #3	$145.53	6.458%	$154.9283	$154.93	$154.95	$154.90
Purchase #4	$170.96	7.802%	$184.2983	$184.30	$184.30	$184.30
Purchase #5	$54.64	9.539%	$59.8521	$59.85	$59.85	$59.90
Purchase #6	$47.74	13.801%	$54.3286	$54.33	$54.35	$54.30
Purchase #7	$180.25	6.856%	$192.6079	$192.61	$192.60	$192.60
7 purchase totals =	$826.60		$888.0898	$888.10	$888.15	$888.10