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	$59.61	13.695%	$67.7736	$67.77	$67.75	$67.80
Purchase #2	$131.62	11.842%	$147.2064	$147.21	$147.20	$147.20
Purchase #3	$63.99	13.700%	$72.7566	$72.76	$72.75	$72.80
Purchase #4	$241.97	12.176%	$271.4323	$271.43	$271.45	$271.40
Purchase #5	$142.46	5.806%	$150.7312	$150.73	$150.75	$150.70
Purchase #6	$237.80	10.769%	$263.4087	$263.41	$263.40	$263.40
Purchase #7	$143.88	10.682%	$159.2493	$159.25	$159.25	$159.20
7 purchase totals =	$1,021.33		$1,132.5581	$1,132.56	$1,132.55	$1,132.50