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	$249.86	3.620%	$258.9049	$258.90	$258.90	$258.90
Purchase #2	$35.59	9.279%	$38.8924	$38.89	$38.90	$38.90
Purchase #3	$50.36	6.712%	$53.7402	$53.74	$53.75	$53.70
Purchase #4	$62.28	5.197%	$65.5167	$65.52	$65.50	$65.50
Purchase #5	$145.55	8.207%	$157.4953	$157.50	$157.50	$157.50
Purchase #6	$231.84	11.868%	$259.3548	$259.35	$259.35	$259.40
Purchase #7	$219.43	3.704%	$227.5577	$227.56	$227.55	$227.60
7 purchase totals =	$994.91		$1,061.4620	$1,061.46	$1,061.45	$1,061.50