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	$176.33	3.564%	$182.6144	$182.61	$182.60	$182.60
Purchase #2	$6.64	12.343%	$7.4596	$7.46	$7.45	$7.50
Purchase #3	$132.53	6.324%	$140.9112	$140.91	$140.90	$140.90
Purchase #4	$241.95	5.140%	$254.3862	$254.39	$254.40	$254.40
Purchase #5	$48.45	5.640%	$51.1826	$51.18	$51.20	$51.20
Purchase #6	$79.73	11.696%	$89.0552	$89.06	$89.05	$89.10
Purchase #7	$162.49	12.287%	$182.4551	$182.46	$182.45	$182.50
7 purchase totals =	$848.12		$908.0643	$908.07	$908.05	$908.20