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	$74.59	3.347%	$77.0865	$77.09	$77.10	$77.10
Purchase #2	$7.25	9.510%	$7.9395	$7.94	$7.95	$7.90
Purchase #3	$194.43	9.736%	$213.3597	$213.36	$213.35	$213.40
Purchase #4	$174.43	6.234%	$185.304	$185.30	$185.30	$185.30
Purchase #5	$236.93	13.768%	$269.5505	$269.55	$269.55	$269.60
Purchase #6	$119.67	10.221%	$131.9015	$131.90	$131.90	$131.90
Purchase #7	$92.62	3.316%	$95.6913	$95.69	$95.70	$95.70
7 purchase totals =	$899.92		$980.8330	$980.83	$980.85	$980.90