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	$202.53	6.372%	$215.4352	$215.44	$215.45	$215.40
Purchase #2	$100.90	4.445%	$105.385	$105.39	$105.40	$105.40
Purchase #3	$172.80	6.291%	$183.6708	$183.67	$183.65	$183.70
Purchase #4	$108.33	9.796%	$118.942	$118.94	$118.95	$118.90
Purchase #5	$148.58	9.430%	$162.5911	$162.59	$162.60	$162.60
Purchase #6	$139.77	5.654%	$147.6726	$147.67	$147.65	$147.70
Purchase #7	$241.61	9.638%	$264.8964	$264.90	$264.90	$264.90
7 purchase totals =	$1,114.52		$1,198.5931	$1,198.60	$1,198.60	$1,198.60