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	$91.69	10.593%	$101.4027	$101.40	$101.40	$101.40
Purchase #2	$107.49	9.724%	$117.9423	$117.94	$117.95	$117.90
Purchase #3	$139.25	12.309%	$156.3903	$156.39	$156.40	$156.40
Purchase #4	$48.47	9.612%	$53.1289	$53.13	$53.15	$53.10
Purchase #5	$62.73	7.627%	$67.5144	$67.51	$67.50	$67.50
Purchase #6	$97.53	13.152%	$110.3571	$110.36	$110.35	$110.40
Purchase #7	$91.85	6.174%	$97.5208	$97.52	$97.50	$97.50
7 purchase totals =	$639.01		$704.2565	$704.25	$704.25	$704.20