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	$127.31	10.803%	$141.0633	$141.06	$141.05	$141.10
Purchase #2	$30.98	5.150%	$32.5755	$32.58	$32.60	$32.60
Purchase #3	$39.78	7.786%	$42.8773	$42.88	$42.90	$42.90
Purchase #4	$43.38	7.448%	$46.6109	$46.61	$46.60	$46.60
Purchase #5	$96.37	10.430%	$106.4214	$106.42	$106.40	$106.40
Purchase #6	$128.90	13.169%	$145.8748	$145.87	$145.85	$145.90
Purchase #7	$160.94	11.344%	$179.197	$179.20	$179.20	$179.20
7 purchase totals =	$627.66		$694.6202	$694.62	$694.60	$694.70