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	$132.96	11.505%	$148.257	$148.26	$148.25	$148.30
Purchase #2	$30.92	5.615%	$32.6562	$32.66	$32.65	$32.70
Purchase #3	$102.67	11.600%	$114.5797	$114.58	$114.60	$114.60
Purchase #4	$57.58	13.850%	$65.5548	$65.55	$65.55	$65.60
Purchase #5	$69.43	5.710%	$73.3945	$73.39	$73.40	$73.40
Purchase #6	$92.93	9.179%	$101.46	$101.46	$101.45	$101.50
Purchase #7	$127.84	7.584%	$137.5354	$137.54	$137.55	$137.50
7 purchase totals =	$614.33		$673.4376	$673.44	$673.45	$673.60