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	$133.97	5.139%	$140.8547	$140.85	$140.85	$140.90
Purchase #2	$143.26	5.225%	$150.7453	$150.75	$150.75	$150.70
Purchase #3	$170.62	5.476%	$179.9632	$179.96	$179.95	$180.00
Purchase #4	$222.86	9.642%	$244.3482	$244.35	$244.35	$244.30
Purchase #5	$98.49	11.256%	$109.576	$109.58	$109.60	$109.60
Purchase #6	$213.42	6.342%	$226.9551	$226.96	$226.95	$227.00
Purchase #7	$91.76	12.650%	$103.3676	$103.37	$103.35	$103.40
7 purchase totals =	$1,074.38		$1,155.8101	$1,155.82	$1,155.80	$1,155.90