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	$169.99	3.457%	$175.8666	$175.87	$175.85	$175.90
Purchase #2	$141.78	11.708%	$158.3796	$158.38	$158.40	$158.40
Purchase #3	$96.41	13.664%	$109.5835	$109.58	$109.60	$109.60
Purchase #4	$236.39	3.741%	$245.2333	$245.23	$245.25	$245.20
Purchase #5	$219.50	4.277%	$228.888	$228.89	$228.90	$228.90
Purchase #6	$94.59	9.806%	$103.8655	$103.87	$103.85	$103.90
Purchase #7	$158.89	6.282%	$168.8715	$168.87	$168.85	$168.90
7 purchase totals =	$1,117.55		$1,190.6880	$1,190.69	$1,190.70	$1,190.80