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	$40.57	7.855%	$43.7568	$43.76	$43.75	$43.80
Purchase #2	$39.89	4.762%	$41.7896	$41.79	$41.80	$41.80
Purchase #3	$69.40	10.766%	$76.8716	$76.87	$76.85	$76.90
Purchase #4	$185.86	13.352%	$210.676	$210.68	$210.70	$210.70
Purchase #5	$60.72	11.508%	$67.7077	$67.71	$67.70	$67.70
Purchase #6	$204.25	11.196%	$227.1178	$227.12	$227.10	$227.10
Purchase #7	$198.62	12.284%	$223.0185	$223.02	$223.00	$223.00
7 purchase totals =	$799.31		$890.9380	$890.95	$890.90	$891.00