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	$135.58	4.646%	$141.879	$141.88	$141.90	$141.90
Purchase #2	$183.97	8.755%	$200.0766	$200.08	$200.10	$200.10
Purchase #3	$97.81	8.437%	$106.0622	$106.06	$106.05	$106.10
Purchase #4	$200.39	9.231%	$218.888	$218.89	$218.90	$218.90
Purchase #5	$131.93	10.267%	$145.4753	$145.48	$145.50	$145.50
Purchase #6	$250.66	5.607%	$264.7145	$264.71	$264.70	$264.70
Purchase #7	$35.59	6.194%	$37.7944	$37.79	$37.80	$37.80
7 purchase totals =	$1,035.93		$1,114.8900	$1,114.89	$1,114.95	$1,115.00