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	$92.55	3.552%	$95.8374	$95.84	$95.85	$95.80
Purchase #2	$83.46	8.253%	$90.348	$90.35	$90.35	$90.30
Purchase #3	$111.29	12.214%	$124.883	$124.88	$124.90	$124.90
Purchase #4	$195.37	3.149%	$201.5222	$201.52	$201.50	$201.50
Purchase #5	$229.48	4.742%	$240.3619	$240.36	$240.35	$240.40
Purchase #6	$206.59	8.176%	$223.4808	$223.48	$223.50	$223.50
Purchase #7	$129.72	10.103%	$142.8256	$142.83	$142.85	$142.80
7 purchase totals =	$1,048.46		$1,119.2589	$1,119.26	$1,119.30	$1,119.20