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	$95.46	10.234%	$105.2294	$105.23	$105.25	$105.20
Purchase #2	$131.69	4.109%	$137.1011	$137.10	$137.10	$137.10
Purchase #3	$68.94	4.271%	$71.8844	$71.88	$71.90	$71.90
Purchase #4	$164.79	12.206%	$184.9043	$184.90	$184.90	$184.90
Purchase #5	$248.81	5.122%	$261.554	$261.55	$261.55	$261.60
Purchase #6	$66.29	10.185%	$73.0416	$73.04	$73.05	$73.00
Purchase #7	$211.64	5.595%	$223.4813	$223.48	$223.50	$223.50
7 purchase totals =	$987.62		$1,057.1961	$1,057.18	$1,057.25	$1,057.20