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	$167.27	13.166%	$189.2928	$189.29	$189.30	$189.30
Purchase #2	$101.30	8.103%	$109.5083	$109.51	$109.50	$109.50
Purchase #3	$176.55	6.793%	$188.543	$188.54	$188.55	$188.50
Purchase #4	$45.39	3.670%	$47.0558	$47.06	$47.05	$47.10
Purchase #5	$172.83	11.361%	$192.4652	$192.47	$192.45	$192.50
Purchase #6	$63.57	9.591%	$69.667	$69.67	$69.65	$69.70
Purchase #7	$158.91	10.823%	$176.1088	$176.11	$176.10	$176.10
7 purchase totals =	$885.82		$972.6409	$972.65	$972.60	$972.70