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	$186.88	3.266%	$192.9835	$192.98	$193.00	$193.00
Purchase #2	$169.69	9.546%	$185.8886	$185.89	$185.90	$185.90
Purchase #3	$18.65	6.603%	$19.8815	$19.88	$19.90	$19.90
Purchase #4	$188.48	11.592%	$210.3286	$210.33	$210.35	$210.30
Purchase #5	$107.77	4.504%	$112.624	$112.62	$112.60	$112.60
Purchase #6	$69.69	12.480%	$78.3873	$78.39	$78.40	$78.40
Purchase #7	$223.50	3.301%	$230.8777	$230.88	$230.90	$230.90
7 purchase totals =	$964.66		$1,030.9712	$1,030.97	$1,031.05	$1,031.00