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	$164.62	8.829%	$179.1543	$179.15	$179.15	$179.20
Purchase #2	$37.95	11.691%	$42.3867	$42.39	$42.40	$42.40
Purchase #3	$250.49	8.302%	$271.2857	$271.29	$271.30	$271.30
Purchase #4	$146.26	6.691%	$156.0463	$156.05	$156.05	$156.00
Purchase #5	$63.75	3.384%	$65.9073	$65.91	$65.90	$65.90
Purchase #6	$165.96	12.216%	$186.2337	$186.23	$186.25	$186.20
Purchase #7	$164.79	4.291%	$171.8611	$171.86	$171.85	$171.90
7 purchase totals =	$993.82		$1,072.8751	$1,072.88	$1,072.90	$1,072.90