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	$98.98	6.738%	$105.6493	$105.65	$105.65	$105.60
Purchase #2	$250.81	6.837%	$267.9579	$267.96	$267.95	$268.00
Purchase #3	$78.90	7.704%	$84.9785	$84.98	$85.00	$85.00
Purchase #4	$82.40	4.311%	$85.9523	$85.95	$85.95	$86.00
Purchase #5	$229.50	3.749%	$238.104	$238.10	$238.10	$238.10
Purchase #6	$84.96	5.810%	$89.8962	$89.90	$89.90	$89.90
Purchase #7	$220.29	9.642%	$241.5304	$241.53	$241.55	$241.50
7 purchase totals =	$1,045.84		$1,114.0686	$1,114.07	$1,114.10	$1,114.10