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	$38.31	5.835%	$40.5454	$40.55	$40.55	$40.50
Purchase #2	$82.32	3.342%	$85.0711	$85.07	$85.05	$85.10
Purchase #3	$100.86	3.372%	$104.261	$104.26	$104.25	$104.30
Purchase #4	$37.67	4.686%	$39.4352	$39.44	$39.45	$39.40
Purchase #5	$162.44	11.598%	$181.2798	$181.28	$181.30	$181.30
Purchase #6	$241.84	9.451%	$264.6963	$264.70	$264.70	$264.70
Purchase #7	$71.29	6.866%	$76.1848	$76.18	$76.20	$76.20
7 purchase totals =	$734.73		$791.4736	$791.48	$791.50	$791.50