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	$178.37	3.212%	$184.0992	$184.10	$184.10	$184.10
Purchase #2	$25.60	7.524%	$27.5261	$27.53	$27.55	$27.50
Purchase #3	$128.35	5.732%	$135.707	$135.71	$135.70	$135.70
Purchase #4	$159.66	7.152%	$171.0789	$171.08	$171.10	$171.10
Purchase #5	$29.26	11.454%	$32.6114	$32.61	$32.60	$32.60
Purchase #6	$73.54	12.660%	$82.8502	$82.85	$82.85	$82.90
Purchase #7	$75.31	4.169%	$78.4497	$78.45	$78.45	$78.40
7 purchase totals =	$670.09		$712.3225	$712.33	$712.35	$712.30