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	$104.60	4.279%	$109.0758	$109.08	$109.10	$109.10
Purchase #2	$81.85	10.140%	$90.1496	$90.15	$90.15	$90.10
Purchase #3	$205.48	5.387%	$216.5492	$216.55	$216.55	$216.50
Purchase #4	$140.26	6.508%	$149.3881	$149.39	$149.40	$149.40
Purchase #5	$237.56	12.133%	$266.3832	$266.38	$266.40	$266.40
Purchase #6	$146.99	3.232%	$151.7407	$151.74	$151.75	$151.70
Purchase #7	$90.58	10.661%	$100.2367	$100.24	$100.25	$100.20
7 purchase totals =	$1,007.32		$1,083.5233	$1,083.53	$1,083.60	$1,083.40