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	$23.31	5.531%	$24.5993	$24.60	$24.60	$24.60
Purchase #2	$81.34	6.873%	$86.9305	$86.93	$86.95	$86.90
Purchase #3	$231.90	6.724%	$247.493	$247.49	$247.50	$247.50
Purchase #4	$181.83	5.459%	$191.7561	$191.76	$191.75	$191.80
Purchase #5	$144.28	11.111%	$160.311	$160.31	$160.30	$160.30
Purchase #6	$198.65	4.730%	$208.0461	$208.05	$208.05	$208.00
Purchase #7	$80.94	5.469%	$85.3666	$85.37	$85.35	$85.40
7 purchase totals =	$942.25		$1,004.5026	$1,004.51	$1,004.50	$1,004.50