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	$96.79	13.615%	$109.968	$109.97	$109.95	$110.00
Purchase #2	$99.51	6.174%	$105.6537	$105.65	$105.65	$105.70
Purchase #3	$177.42	9.726%	$194.6759	$194.68	$194.70	$194.70
Purchase #4	$12.39	4.234%	$12.9146	$12.91	$12.90	$12.90
Purchase #5	$39.83	10.150%	$43.8727	$43.87	$43.85	$43.90
Purchase #6	$162.69	11.483%	$181.3717	$181.37	$181.35	$181.40
Purchase #7	$47.25	13.360%	$53.5626	$53.56	$53.55	$53.60
7 purchase totals =	$635.88		$702.0192	$702.01	$701.95	$702.20