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	$140.35	8.277%	$151.9668	$151.97	$151.95	$152.00
Purchase #2	$81.81	10.654%	$90.526	$90.53	$90.55	$90.50
Purchase #3	$190.43	13.142%	$215.4563	$215.46	$215.45	$215.50
Purchase #4	$35.60	6.794%	$38.0187	$38.02	$38.00	$38.00
Purchase #5	$55.96	12.485%	$62.9466	$62.95	$62.95	$62.90
Purchase #6	$54.74	9.165%	$59.7569	$59.76	$59.75	$59.80
Purchase #7	$123.61	3.843%	$128.3603	$128.36	$128.35	$128.40
7 purchase totals =	$682.50		$747.0316	$747.05	$747.00	$747.10