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	$89.90	6.858%	$96.0653	$96.07	$96.05	$96.10
Purchase #2	$38.87	4.347%	$40.5597	$40.56	$40.55	$40.60
Purchase #3	$119.37	10.130%	$131.4622	$131.46	$131.45	$131.50
Purchase #4	$165.46	12.703%	$186.4784	$186.48	$186.50	$186.50
Purchase #5	$54.25	5.700%	$57.3423	$57.34	$57.35	$57.30
Purchase #6	$240.29	9.196%	$262.3871	$262.39	$262.40	$262.40
Purchase #7	$224.86	9.543%	$246.3184	$246.32	$246.30	$246.30
7 purchase totals =	$933.00		$1,020.6134	$1,020.62	$1,020.60	$1,020.70