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	$174.68	12.426%	$196.3857	$196.39	$196.40	$196.40
Purchase #2	$143.88	5.712%	$152.0984	$152.10	$152.10	$152.10
Purchase #3	$146.68	6.621%	$156.3917	$156.39	$156.40	$156.40
Purchase #4	$20.26	5.206%	$21.3147	$21.31	$21.30	$21.30
Purchase #5	$10.70	6.407%	$11.3855	$11.39	$11.40	$11.40
Purchase #6	$70.34	8.199%	$76.1072	$76.11	$76.10	$76.10
Purchase #7	$49.36	3.803%	$51.2372	$51.24	$51.25	$51.20
7 purchase totals =	$615.90		$664.9204	$664.93	$664.95	$664.90