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	$79.44	9.296%	$86.8247	$86.82	$86.80	$86.80
Purchase #2	$143.75	3.593%	$148.9149	$148.91	$148.90	$148.90
Purchase #3	$122.36	9.546%	$134.0405	$134.04	$134.05	$134.00
Purchase #4	$97.63	6.158%	$103.6421	$103.64	$103.65	$103.60
Purchase #5	$154.88	10.544%	$171.2105	$171.21	$171.20	$171.20
Purchase #6	$229.90	12.433%	$258.4835	$258.48	$258.50	$258.50
Purchase #7	$150.94	11.414%	$168.1683	$168.17	$168.15	$168.20
7 purchase totals =	$978.90		$1,071.2845	$1,071.27	$1,071.25	$1,071.20