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	$136.57	4.734%	$143.0352	$143.04	$143.05	$143.00
Purchase #2	$161.89	6.542%	$172.4808	$172.48	$172.50	$172.50
Purchase #3	$73.97	12.543%	$83.2481	$83.25	$83.25	$83.20
Purchase #4	$121.43	12.800%	$136.973	$136.97	$136.95	$137.00
Purchase #5	$165.35	11.813%	$184.8828	$184.88	$184.90	$184.90
Purchase #6	$55.25	12.317%	$62.0551	$62.06	$62.05	$62.10
Purchase #7	$131.37	12.442%	$147.7151	$147.72	$147.70	$147.70
7 purchase totals =	$845.83		$930.3901	$930.40	$930.40	$930.40