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	$26.92	10.313%	$29.6963	$29.70	$29.70	$29.70
Purchase #2	$183.34	7.399%	$196.9053	$196.91	$196.90	$196.90
Purchase #3	$70.92	7.634%	$76.334	$76.33	$76.35	$76.30
Purchase #4	$150.91	7.361%	$162.0185	$162.02	$162.00	$162.00
Purchase #5	$129.30	11.137%	$143.7001	$143.70	$143.70	$143.70
Purchase #6	$49.34	3.614%	$51.1231	$51.12	$51.10	$51.10
Purchase #7	$112.88	9.607%	$123.7244	$123.72	$123.70	$123.70
7 purchase totals =	$723.61		$783.5017	$783.50	$783.45	$783.40