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	$68.90	13.731%	$78.3607	$78.36	$78.35	$78.40
Purchase #2	$71.89	9.648%	$78.8259	$78.83	$78.85	$78.80
Purchase #3	$155.67	11.813%	$174.0593	$174.06	$174.05	$174.10
Purchase #4	$134.88	5.737%	$142.6181	$142.62	$142.60	$142.60
Purchase #5	$182.48	4.104%	$189.969	$189.97	$189.95	$190.00
Purchase #6	$208.76	7.632%	$224.6926	$224.69	$224.70	$224.70
Purchase #7	$238.33	6.142%	$252.9682	$252.97	$252.95	$253.00
7 purchase totals =	$1,060.91		$1,141.4938	$1,141.50	$1,141.45	$1,141.60