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	$142.60	8.414%	$154.5984	$154.60	$154.60	$154.60
Purchase #2	$166.52	11.403%	$185.5083	$185.51	$185.50	$185.50
Purchase #3	$144.33	5.632%	$152.4587	$152.46	$152.45	$152.50
Purchase #4	$204.90	5.103%	$215.356	$215.36	$215.35	$215.40
Purchase #5	$237.45	7.530%	$255.33	$255.33	$255.35	$255.30
Purchase #6	$18.69	4.788%	$19.5849	$19.58	$19.60	$19.60
Purchase #7	$146.35	11.529%	$163.2227	$163.22	$163.20	$163.20
7 purchase totals =	$1,060.84		$1,146.0590	$1,146.06	$1,146.05	$1,146.10